|
Stockholders' Equity - Summary of Authorized and Outstanding Equity (Parenthetical) (Detail) (USD $)
|
9 Months Ended | 9 Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Sep. 30, 2014
|
Dec. 31, 2012
|
Sep. 30, 2014
Class A Common Stock
|
Dec. 31, 2013
Class A Common Stock
|
Sep. 30, 2013
Class A Common Stock
|
Jul. 12, 2013
Class A Common Stock
|
Dec. 31, 2012
Class A Common Stock
|
Sep. 30, 2014
Class B Common Stock
|
May 31, 2014
Class B Common Stock
|
Feb. 28, 2014
Class B Common Stock
|
Dec. 31, 2013
Class B Common Stock
|
Sep. 30, 2013
Class B Common Stock
|
Dec. 31, 2012
Class B Common Stock
|
|
| Class Of Stock [Line Items] | |||||||||||||
| Common stock, par value | $ 0.01 | $ 0.01 | $ 0.01 | $ 17.73 | $ 14.50 | $ 0.01 | |||||||
| Preferred stock, par value | $ 0.01 | ||||||||||||
| Common stock, voting rights | 1 vote per share | 1 vote per share | |||||||||||
| Common stockholders rights percentage | 100.00% | ||||||||||||
| Class of share exchangeable to another class | one share of Class A common stock | ||||||||||||
| Common stock, shares outstanding | 7,658,010 | 7,522,974 | 5,509,000 | 5,509,297 | 4,570,413 | 4,464,617 | 6,462,000 | ||||||
| Deferred equity units exercisable | 52,188 |