CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance at beginning of period at Dec. 31, 2012	$ 2,131,447	$ 42,086	$ (3,349)	$ 695,566	$ 23,880	$ 1,373,264
Balance (in shares) at Dec. 31, 2012		420,861,000	808,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)	279,773					279,773
Exercise of stock appreciation rights	(13,226)	$ 38		(13,264)
Exercise of stock appreciation rights (in shares)		382,000
Stock amortization and vesting	9,802	$ 77		9,725
Stock amortization and vesting (in shares)		772,000
Tax benefit of stock-based compensation	18,913			18,913
Purchase of treasury stock	$ (164,634)		$ (164,634)
Purchase of treasury stock (in shares)	4,800,000		4,810,000
Cash dividends at $0.08, $0.08 and $0.06 per share for the year ended December 31, 2015, 2014 and 2013, respectively	$ (25,232)					(25,232)
Other comprehensive income (loss)	(32,241)				(32,241)
Balance at end of period at Dec. 31, 2013	2,204,602	$ 42,201	$ (167,983)	710,940	(8,361)	1,627,805
Balance (in shares) at Dec. 31, 2013		422,015,000	5,618,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)	104,468					104,468
Stock amortization and vesting	958	$ 91		867
Stock amortization and vesting (in shares)		900,000
Tax benefit of stock-based compensation	(1,375)			(1,375)
Purchase of treasury stock	$ (138,852)		$ (138,852)
Purchase of treasury stock (in shares)	4,300,000		4,275,000
Cash dividends at $0.08, $0.08 and $0.06 per share for the year ended December 31, 2015, 2014 and 2013, respectively	$ (33,278)					(33,278)
Other comprehensive income (loss)	6,210				6,210
Balance at end of period at Dec. 31, 2014	2,142,733	$ 42,292	$ (306,835)	710,432	(2,151)	1,698,995
Balance (in shares) at Dec. 31, 2014		422,915,000	9,893,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(113,891)					(113,891)
Exercise of stock appreciation rights	(942)	$ 4		(946)
Exercise of stock appreciation rights (in shares)		40,000
Stock amortization and vesting	$ 12,592	$ 81		12,511
Stock amortization and vesting (in shares)		814,000
Purchase of treasury stock (in shares)	0
Cash dividends at $0.08, $0.08 and $0.06 per share for the year ended December 31, 2015, 2014 and 2013, respectively	$ (33,090)					(33,090)
Other comprehensive income (loss)	1,786				1,786
Balance at end of period at Dec. 31, 2015	$ 2,009,188	$ 42,377	$ (306,835)	$ 721,997	$ (365)	$ 1,552,014
Balance (in shares) at Dec. 31, 2015		423,769,000	9,893,000