Shareholders' Equity - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	Oct. 26, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Aug. 10, 2017	Dec. 31, 2016	Aug. 14, 2015
Equity, Class of Treasury Stock [Line Items]
Aggregate purchase price				$ 25,065,000	$ 70,428,000
Shares of common stock purchased from restricted stock award related to recipients' employment tax obligations				308,801	255,164
Repurchase of common stock for employee tax withholding				$ 22,600,000	$ 10,700,000
Reissuance of treasury shares as a result of employee vesting				850,925	731,758
Cash dividends paid				$ 14,200,000
Cash dividends declared		$ 0.31	$ 0	$ 0.9375	$ 0
Noncontrolling interests proportionate share of equity		$ 48,519,000		$ 48,519,000			$ 57,016,000
Other comprehensive income or loss attributed to noncontrolling interests				0	$ 0
Merchant banking funds
Equity, Class of Treasury Stock [Line Items]
Noncontrolling interests proportionate share of equity		35,100,000		35,100,000			35,000,000
Municipal bond fund with employee investors
Equity, Class of Treasury Stock [Line Items]
Noncontrolling interests proportionate share of equity							9,200,000
Senior living fund
Equity, Class of Treasury Stock [Line Items]
Noncontrolling interests proportionate share of equity		$ 13,400,000		$ 13,400,000			$ 12,800,000
Share Repurchase Program Authorized 2015
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock, authorized amount								$ 150,000,000
Shares repurchased				36,936	1,536,226
Average share price				$ 67.62	$ 38.89
Aggregate purchase price				$ 2,500,000	$ 59,700,000
Share Repurchase Program Authorized 2017
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock, authorized amount						$ 150,000,000
Cash dividends declared
Equity, Class of Treasury Stock [Line Items]
Cash dividends declared	$ 0.3125