Consolidated Statement of Changes in Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock
Beginning Balance at Dec. 31, 2012	$ 2,640,657	$ 1,841	$ 863,558	$ 2,548,542	$ 21,767	$ (795,051)
Beginning Balance (in shares) at Dec. 31, 2012	184,059,900	184,060,000
Net income	171,418			171,418
Foreign currency translation adjustment	(3,668)				(3,668)
Issuance of restricted stock (in shares)		1,312,000
Issuance of restricted stock		13	(13)
Vesting of stock unit awards		9,000
Forfeitures of restricted stock (in shares)		(56,000)
Forfeitures of restricted stock		(1)	1
Exercise of stock options (in shares)	1,190,000	1,190,000
Exercise of stock options	19,286	12	19,274
Stock-based compensation	19,028		19,028
Tax benefit related to stock-based compensation	4,791		4,791
Payment of cash dividends	(21,904)			(21,904)
Purchase of treasury stock	(85,733)					(85,733)
Ending Balance at Sep. 30, 2013	$ 2,743,875	$ 1,865	$ 906,639	$ 2,698,056	$ 18,099	$ (880,784)
Ending Balance (in shares) at Sep. 30, 2013	186,515,121	186,515,000