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, 2013					$ (15,859)
Increase (Decrease) in Stockholders' Equity
Net income						$ 232,438
Other comprehensive loss					(2,544)
Balance at the end of the period at Sep. 30, 2014					(18,403)
Balance at the beginning of the period at Jun. 30, 2014					(13,756)
Increase (Decrease) in Stockholders' Equity
Net income						74,586
Other comprehensive loss					(4,647)
Balance at the end of the period at Sep. 30, 2014					(18,403)
Balance at the beginning of the period at Dec. 31, 2014	$ 997	$ 318,636	$ 1,041,909	$ (525,015)	(50,443)	786,084
Balance (in shares) at Dec. 31, 2014	99,701
Increase (Decrease) in Stockholders' Equity
Net income			182,616			182,616
Recognition of equity compensation		35,880				35,880
Net issuance/forfeiture of nonvested shares		(29,039)		29,039
Dividends accrued, $1.29 per share			(108,002)			(108,002)
Excess tax benefits from share-based payment arrangements		5,357				5,357
Repurchase of common stock				(63,277)		(63,277)
Other comprehensive loss					(1,721)	(1,721)
Balance at the end of the period at Sep. 30, 2015	$ 997	330,834	1,116,523	(559,253)	(52,164)	836,937
Balance (in shares) at Sep. 30, 2015	99,701
Balance at the beginning of the period at Jun. 30, 2015					(51,731)
Increase (Decrease) in Stockholders' Equity
Net income						48,058
Other comprehensive loss					(433)
Balance at the end of the period at Sep. 30, 2015	$ 997	$ 330,834	$ 1,116,523	$ (559,253)	$ (52,164)	$ 836,937
Balance (in shares) at Sep. 30, 2015	99,701