Consolidated Statements Of Stockholders' Equity (USD $) In Thousands, except Share data	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balances at Dec. 31, 2008	$ 1,116	$ 560,072	$ 467,138		$ 1,028,326
Balances, shares at Dec. 31, 2008	111,589,000
Exercise of stock options (Note 12)	29	54,804			54,833
Exercise of stock options (Note 12), shares	2,903,000				2,903,000
Shares issued through ESPP	1	1,181			1,182
Shares issued through ESPP, shares	93,000				93,390
Issuance of restricted stock	17	(6)			11
Issuance of restricted stock, shares	1,713,000
Forfeitures of restricted stock, shares	(24,000)
Common stock acquired				(343,250)	(343,250)
Common stock retired	(183)	(8,115)	(334,952)	343,250
Common stock retired, shares	(18,246,000)
Stock-based compensation expense		25,516			25,516
Tax benefit for exercise of employee stock awards (Notes 9 and 12)		4,448			4,448
Tax effect of cancelled options		(5,273)			(5,273)
Convertible debt permanent tax effect		26			26
Net income			136,096		136,096
Balances at Dec. 31, 2009	980	632,653	268,282		901,915
Balances, shares at Dec. 31, 2009	98,028,000
Exercise of stock options (Note 12)	11	25,525			25,536
Exercise of stock options (Note 12), shares	1,070,000				1,069,537
Shares issued through ESPP	1	1,281			1,282
Shares issued through ESPP, shares	63,000				62,739
Issuance of restricted stock	6	(2)			4
Issuance of restricted stock, shares	582,000
Forfeitures of restricted stock, shares	(20,000)
Common stock acquired				(99,961)	(99,961)
Common stock retired	(35)	(4,104)	(95,822)	99,961
Common stock retired, shares	(3,450,000)
Stock-based compensation expense		25,244			25,244
Tax benefit for exercise of employee stock awards (Notes 9 and 12)		1,419			1,419
Fractional share settlements		(54)			(54)
Fractional shares settlements, shares	(3,000)
Convertible debt permanent tax effect		26			26
Cash dividends declared (Note 11)			(39,236)		(39,236)
Net income			181,574		181,574
Balances at Dec. 31, 2010	963	681,988	314,798		997,749
Balances, shares at Dec. 31, 2010	96,270,000
Exercise of stock options (Note 12)	6	13,030			13,036
Exercise of stock options (Note 12), shares	597,000				596,682
Shares issued through ESPP	1	1,514			1,515
Shares issued through ESPP, shares	73,000				73,674
Issuance of restricted stock	2				2
Issuance of restricted stock, shares	272,000
Forfeitures of restricted stock, shares	(34,000)
Common stock acquired				(249,986)	(249,986)
Common stock retired	(102)	(10,659)	(239,225)	249,986
Common stock retired, shares	(10,151,000)
Stock-based compensation expense		20,766			20,766
Tax benefit for exercise of employee stock awards (Notes 9 and 12)		415			415
Convertible debt permanent tax effect		26			26
Cash dividends declared (Note 11)			(74,920)		(74,920)
Net income			177,311		177,311
Balances at Dec. 31, 2011	$ 870	$ 707,080	$ 177,964		$ 885,914
Balances, shares at Dec. 31, 2011	87,027,000