Consolidated Statement of Stockholders’ Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income(Loss)	Total
Balance at the beginning of the period at Dec. 31, 2014					$ (50,443)
Increase (Decrease) in Stockholders' Equity
Net income						$ 182,616
Other comprehensive income					(1,721)
Balance at the end of the period at Sep. 30, 2015					(52,164)
Balance at the beginning of the period at Jun. 30, 2015					(51,731)
Increase (Decrease) in Stockholders' Equity
Net income						48,058
Other comprehensive income					(433)
Balance at the end of the period at Sep. 30, 2015					(52,164)
Balance at the beginning of the period at Dec. 31, 2015	$ 997	$ 331,611	$ 1,141,608	$ (566,256)	(61,505)	846,455
Balance (in shares) at Dec. 31, 2015	99,701
Increase (Decrease) in Stockholders' Equity
Net income			124,490			124,490
Recognition of equity compensation		38,573				38,573
Net issuance/forfeiture of nonvested shares		(72,229)		72,229
Dividends accrued, $1.38 per share			(114,722)			(114,722)
Tax impact of share-based payment arrangements		(4,821)				(4,821)
Repurchase of common stock				(47,984)		(47,984)
Other comprehensive income					3,486	3,486
Balance at the end of the period at Sep. 30, 2016	$ 997	293,134	1,151,376	(542,011)	(58,019)	845,477
Balance (in shares) at Sep. 30, 2016	99,701
Increase (Decrease) in Redeemable Noncontrolling Interest
Adoption of consolidation guidance on January 1, 2016 - redeemable noncontrolling interests in sponsored funds						14,330
Net income						1,355
Net redemption of redeemable noncontrolling interests in sponsored funds						(5,313)
Balance at the end of the period at Sep. 30, 2016						10,372
Balance at the beginning of the period at Jun. 30, 2016					(57,508)
Increase (Decrease) in Stockholders' Equity
Net income						53,827
Other comprehensive income					(511)
Balance at the end of the period at Sep. 30, 2016	$ 997	$ 293,134	$ 1,151,376	$ (542,011)	$ (58,019)	845,477
Balance (in shares) at Sep. 30, 2016	99,701
Balance at the end of the period at Sep. 30, 2016						$ 10,372