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 (Loss) [Member]	Treasury Stock [Member]	Total
Balances at Dec. 31, 2010	$ 472	$ 820,237	$ 158,749	$ 4,884	$ (659)	$ 983,683
Balances, shares (in Shares) at Dec. 31, 2010	47,198,081				(55,623)
Reinstatement of tax benefits on non-qualified stock options exercised in previous years (Footnote 13)		18,423				18,423
Net income (loss)			(98,390)			(98,390)
Unrealized gain on available-for-sale investments				(12,124)		(12,124)
Total comprehensive income (loss)						(110,514)
Shares issued upon exercise of stock options and awards of restricted stock	8	9,036				9,044
Shares issued upon exercise of stock options and awards of restricted stock, shares (in Shares)	819,027
Cash dividends paid			(47,432)			(47,432)
Stock-based compensation expense		15,432				15,432
Forfeiture of restricted stock (in Shares)					(4,289)
Balances at Dec. 31, 2011	480	863,128	12,927	(7,240)	(659)	868,636
Balances, shares (in Shares) at Dec. 31, 2011	48,017,108				(59,912)
Reversal of uncertain tax positions due to statute of limitations		1,551				1,551
Retirement of treasury stock	(1)	(659)			659	(1)
Retirement of treasury stock (in Shares)	(62,230)				62,230
Net income (loss)			62,699			62,699
Unrealized gain on available-for-sale investments				12,078		12,078
Total comprehensive income (loss)						74,777
Shares issued upon exercise of stock options and awards of restricted stock	8	16,616				16,624
Shares issued upon exercise of stock options and awards of restricted stock, shares (in Shares)	752,855
Cash dividends paid			(96,915)			(96,915)
Stock-based compensation expense		16,225				16,225
Forfeiture of restricted stock (in Shares)	(8,976)				(2,318)
Balances at Dec. 31, 2012	487	896,861	(21,289)	4,838		880,897
Balances, shares (in Shares) at Dec. 31, 2012	48,698,757
Net income tax deficiency from share-based compensation		(3,540)				(3,540)
Net income (loss)			314,385			314,385
Unrealized gain on available-for-sale investments				6,737		6,737
Total comprehensive income (loss)						321,122
Shares issued upon exercise of stock options and awards of restricted stock	2	5,116				5,118
Shares issued upon exercise of stock options and awards of restricted stock, shares (in Shares)	178,737
Stock-based compensation expense		9,652				9,652
Forfeiture of restricted stock (in Shares)	(88,607)
Forfeiture of restricted stock	(1)	1
Balances at Dec. 31, 2013	$ 488	$ 908,090	$ 293,096	$ 11,575		$ 1,213,249
Balances, shares (in Shares) at Dec. 31, 2013	48,788,887