Stock-Based Compensation - Additional Information (Detail) (USD $)	9 Months Ended				9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Options and Restricted Stock	Sep. 30, 2013 Two Thousand Twelve Incentive Plan	Sep. 30, 2013 Stock Options	Sep. 30, 2013 Restricted Stock	Sep. 30, 2012 Restricted Stock	Sep. 30, 2013 Restricted Stock	Sep. 30, 2012 Restricted Stock	Sep. 30, 2013 Restricted Stock Stock Incentive Plan Twenty Twelve	Sep. 30, 2013 Restricted Stock Stock Incentive Plan Twenty Twelve
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant				16,763,551		11,453
Shares transferred					1,030,673
Shares granted	2,317,522										37,500	2,317,522
Shares granted, weighted average grant date fair value	$ 13.63										$ 14.91	$ 13.63
Shares granted, vesting period									5 years
Compensation and benefits expense							$ 5,700,000	$ 5,100,000	$ 16,600,000	$ 15,500,000
Unrecognized compensation cost relating to unvested restricted stock	60,900,000
Unrecognized compensation cost relating to unvested restricted stock, recognition period (in years)	3 years 3 months 18 days
Stock option plans expiration period from date of grant	10 years
Stock option outstanding	128,561		2,641,344
Intrinsic value of stock options outstanding and exercisable	156,000
Intrinsic values of options exercised	$ 106,000
Stock options exercised	29,618	0