Quarterly report pursuant to Section 13 or 15(d)

Investments and Fair Value Measurements - Category of Financial Instruments Not Held at Fair Value (Detail)

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Investments and Fair Value Measurements - Category of Financial Instruments Not Held at Fair Value (Detail) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Financial Assets, Carrying Amount $ 109,550 $ 112,281
Financial liabilities, Carrying Amount 38,949 46,197
Level II | Notes Payable    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Financial liabilities, Carrying Amount 731 2,486
Financial liabilities, Fair Value 731 2,486
Investments    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Financial Assets, Carrying Amount 13 335
Financial Assets, Fair Value 13 335
Cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Financial Assets, Carrying Amount 39,558 37,517
Financial Assets, Fair Value $ 39,558 $ 37,517