Consolidated Statements Of Stockholders' Equity (USD $) In Thousands, except Share data	Common Stock [Member]	Additional Paid-In-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]	Total
Beginning balances, value at Dec. 31, 2008	$ 467	$ 788,207	$ 292,905		$ (659)	$ 1,080,920
Beginning balances, shares at Dec. 31, 2008	46,715,000				(49,000)
Net (loss) income			24,679			24,679
Shares issued upon exercise of stock options and awards of restricted stock, value	4	3,619				3,623
Shares issued upon exercise of stock options and awards of restricted stock, shares	355,000
Tax benefit of non-qualified stock options exercised		(4,250)				(4,250)
Cash dividends paid			(46,925)			(46,925)
Stock-based compensation expense		15,099				15,099
Forfeitures of restricted stock					(4,000)
Ending balances, value at Dec. 31, 2009	471	802,675	270,659		(659)	1,073,146
Ending balances, shares at Dec. 31, 2009	47,070,000				(53,000)
Net (loss) income			(64,770)			(64,770)
Change in unrealized (loss) gain on available-for-sale investments				4,884		4,884
Total comprehensive loss						(59,886)
Shares issued upon exercise of stock options and awards of restricted stock, value	1	52				53
Shares issued upon exercise of stock options and awards of restricted stock, shares	128,000
Cash dividends paid			(47,140)			(47,140)
Stock-based compensation expense		17,510				17,510
Forfeitures of restricted stock					(3,000)
Ending balances, value at Dec. 31, 2010	472	820,237	158,749	4,884	(659)	983,683
Ending balances, shares at Dec. 31, 2010	47,198,000				(56,000)
Net (loss) income			(98,390)			(98,390)
Change in unrealized (loss) gain on available-for-sale investments				(12,124)		(12,124)
Total comprehensive loss						(110,514)
Shares issued upon exercise of stock options and awards of restricted stock, value	8	9,036				9,044
Shares issued upon exercise of stock options and awards of restricted stock, shares	819,000
Cash dividends paid			(47,432)			(47,432)
Stock-based compensation expense		15,432				15,432
Forfeitures of restricted stock					(4,000)
Reinstatement of tax benefits on non-qualified stock options exercised in previous years (Footnote 7)		18,423				18,423
Ending balances, value at Dec. 31, 2011	$ 480	$ 863,128	$ 12,927	$ (7,240)	$ (659)	$ 868,636
Ending balances, shares at Dec. 31, 2011	48,017,000				(60,000)