Notes Payable, Warrants and Subordinated Borrowings - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands			9 Months Ended
	Nov. 02, 2015	Aug. 21, 2008	Sep. 30, 2015	Nov. 30, 2015	Dec. 31, 2014
Notes Payable And Warrants [Line Items]
Subordinated Borrowings			$ 22,550,000		$ 22,550,000
Subordinated Borrowing, Interest Rate (as a percent)			5.50%
Class A [Member]
Notes Payable And Warrants [Line Items]
Common Stock, Par or Stated Value Per Share (in dollars per share)			$ 0.01		$ 0.01
Maximum percent of voting securities and total shares of class A common stock owned by holder or group of affiliates for warrant transfer (as a percent)			2.00%
Class A [Member] | Maximum [Member]
Notes Payable And Warrants [Line Items]
Percent of outstanding shares of common stock owned by holder or group of affiliates for warrant transfer (as a percent)			25.00%
Class A [Member] | Warrant [Member]
Notes Payable And Warrants [Line Items]
Warrants to purchase Class A shares (in shares)		5,455
Class A Shares purchase price per share (in dollars per share)		$ 22.00
Senior Notes [Member]
Notes Payable And Warrants [Line Items]
Senior Notes		$ 120,000,000
Senior Notes coupon interest (as a percent)		5.20%
Senior notes effective yield (as a percent)			7.94%
Redemption period (in days)			90 days
Event of default under the indenture accreted amount due and payable (as a percent)			33.33%
Maximum percent of aggregate principal amount of senior notes owned by holder or group of affiliates for transfer (as a percent)			15.00%
Subsequent Event [Member]
Notes Payable And Warrants [Line Items]
Cash Received For Settlement Of Warrant				$ 11,000,000
Loans Payable	$ 120,000,000
Loans Payable Final Payment After Closing (in years)	5 years
Strategic Alliance Term (in years)	3 years
Strategic Alliance Automatic Renewals (in years)	1 year
Subsequent Event [Member] | Class A [Member]
Notes Payable And Warrants [Line Items]
Public Offering, Shares				5,455
Public Offering, Shares Offered To Public				3,100
Share Repurchase During Offering				2,355
Subsequent Event [Member] | Class A [Member] | Warrant [Member]
Notes Payable And Warrants [Line Items]
Warrants to purchase Class A shares (in shares)				5,455