Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant	12,245,112		12,245,112
Shares granted			2,335,641
Shares granted, weighted average grant date fair value			$ 15.83
Unrecognized compensation cost relating to unvested restricted stock	$ 78,400,000		$ 78,400,000
Unrecognized compensation cost relating to unvested restricted stock, recognition period (in years)			3 years 2 months 12 days
Stock option plans expiration period from date of grant			10 years
Stock option outstanding	2,400		2,400		58,560
Intrinsic value of stock options outstanding and exercisable	$ 3,000		$ 3,000
Intrinsic values of options exercised				$ 132,000
Stock option Exercised			0
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted, vesting period			5 years
Compensation and benefits expense	$ 8,000,000	$ 6,800,000	$ 22,600,000	$ 20,700,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant	0		0
Two Thousand Twelve Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares transferred			1,030,673
Stock Incentive Plan Twenty Twelve | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	34,500		2,335,641
Shares granted, weighted average grant date fair value	$ 18.02		$ 15.83