Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Beginning balances, value at Dec. 31, 2009	$ 1,073,146	$ 471	$ 802,675	$ 270,659		$ (659)
Beginning balances, shares at Dec. 31, 2009		47,069,561				(52,789)
Net income (loss)	(64,770)			(64,770)
Unrealized gain on available-for-sale investments	4,884				4,884
Comprehensive income (loss)	(59,886)
Shares issued upon exercise of stock options and awards of restricted stock, value	53	1	52
Shares issued upon exercise of stock options and awards of restricted stock, shares		128,520
Cash dividends paid	(47,140)			(47,140)
Stock-based compensation expense	17,510		17,510
Forfeitures of restricted stock						(2,834)
Ending balances, value at Dec. 31, 2010	983,683	472	820,237	158,749	4,884	(659)
Ending balances, shares at Dec. 31, 2010		47,198,081				(55,623)
Net income (loss)	(98,390)			(98,390)
Unrealized gain on available-for-sale investments	(12,124)				(12,124)
Comprehensive income (loss)	(110,514)
Shares issued upon exercise of stock options and awards of restricted stock, value	9,044	8	9,036
Shares issued upon exercise of stock options and awards of restricted stock, shares		819,027
Cash dividends paid	(47,432)			(47,432)
Stock-based compensation expense	15,432		15,432
Forfeitures of restricted stock						(4,289)
Reinstatement of tax benefits on non-qualified stock options exercised in previous years (Footnote 13)	18,423		18,423
Ending balances, value at Dec. 31, 2011	868,636	480	863,128	12,927	(7,240)	(659)
Ending balances, shares at Dec. 31, 2011		48,017,108				(59,912)
Net income (loss)	62,699			62,699
Unrealized gain on available-for-sale investments	12,078				12,078
Comprehensive income (loss)	74,777
Shares issued upon exercise of stock options and awards of restricted stock, value	16,624	8	16,616
Shares issued upon exercise of stock options and awards of restricted stock, shares		752,855
Cash dividends paid	(96,915)			(96,915)
Stock-based compensation expense	16,225		16,225
Reversal of uncertain tax positions due to statute of limitations	1,551		1,551
Retirement of treasury stock	(1)	(1)	(659)			659
Retirement of treasury stock, Shares		(62,230)				62,230
Forfeitures of restricted stock		(8,976)				(2,318)
Ending balances, value at Dec. 31, 2012	$ 880,897	$ 487	$ 896,861	$ (21,289)	$ 4,838
Ending balances, shares at Dec. 31, 2012		48,698,757