Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation - Summary of Equity Grants (Detail)

v2.4.1.9
Equity-Based Compensation - Summary of Equity Grants (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Performance Units    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Units 96,971us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
238,371us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Vested, Units (90,585)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
(140,549)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Forfeited, Units   (851)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Ending Balance, Units 6,386us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
96,971us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Beginning Balance, Range of Fair Value per unit $ 3.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 3.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Ending Balance, Range of Fair Value per unit $ 3.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 3.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Deferred Equity Units    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Units 52,188us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
175,298us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
Vested, Units (47,277)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
(123,110)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
Ending Balance, Units 4,911us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
52,188us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
Deferred Equity Units | Minimum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Range of Fair Value per unit $ 12.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
$ 12.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Vested, Range of Fair Value per unit $ (12.00)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
$ 12.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Ending Balance, Range of Fair Value per unit $ 12.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
$ 12.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Deferred Equity Units | Maximum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Range of Fair Value per unit $ 15.65us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
$ 17.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Vested, Range of Fair Value per unit $ (13.97)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
$ (16.81)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Ending Balance, Range of Fair Value per unit $ 14.25us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
$ 18.29us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember