Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Common Stock [Member] Non Employee [Member]	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Auction Rate Securities [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Available-for-sale Securities [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Auction Rate Securities [Member]	Non Employee [Member]	Available-for-sale Securities [Member]	Total
Balance as of January 1, 2011 at Dec. 31, 2010		$ 178,269	$ 66,647			$ 1,979				$ 246,895
Balance as of January 1, 2011 (in Shares) at Dec. 31, 2010		35,063,000
Net income			13,301							13,301
Change in unrealized gain (loss) on available-for-sale securities				270	(37)		270		(37)
Foreign exchange gain						1,381				1,381
Exercise of stock options, including net excess tax benefit		4,630								4,630
Exercise of stock options, including net excess tax benefit (in Shares)		685,000								685,417
Repurchase of common shares		(38,472)								(38,472)
Repurchase of common shares (in Shares)		(2,485,000)
Shares purchased through ESPP		1,773								1,773
Shares purchased through ESPP (in Shares)		150,000
Stock-based compensation expense, net of forfeitures		13,123								13,123
Compensation expense for non-employee stock options	13							13		13,012
Release of restricted stock upon vesting (in Shares)		413,000
Balance as of at Dec. 31, 2011		159,336	79,948			3,593				242,877
Balance as of (in Shares) at Dec. 31, 2011		33,826,000
Net income			15,756							15,756
Change in unrealized gain (loss) on available-for-sale securities				140	34		140		34	140
Foreign exchange gain						408				408
Cash dividend			(35,664)							(35,664)
Exercise of stock options, including net excess tax benefit		14,232								14,232
Exercise of stock options, including net excess tax benefit (in Shares)		1,152,000								1,151,884
Shares purchased through ESPP		1,852								1,852
Shares purchased through ESPP (in Shares)		152,000
Stock-based compensation expense, net of forfeitures		18,642								18,642
Compensation expense for non-employee stock options	17							17		18,465
Release of restricted stock upon vesting (in Shares)		543,000
Balance as of at Dec. 31, 2012		194,079	60,040			4,175				258,294
Balance as of (in Shares) at Dec. 31, 2012		35,673,000								35,673
Net income			22,898							22,898
Change in unrealized gain (loss) on available-for-sale securities				130	(33)		130		(33)	130
Foreign exchange gain						1,988				1,988
Exercise of stock options, including net excess tax benefit		37,877								37,877
Exercise of stock options, including net excess tax benefit (in Shares)		2,446,000								2,445,523
Repurchase of common shares		(20,615)								(20,615)
Repurchase of common shares (in Shares)		(664,000)
Shares purchased through ESPP		2,145								2,145
Shares purchased through ESPP (in Shares)		111,000
Stock-based compensation expense, net of forfeitures		20,715								20,715
Compensation expense for non-employee stock options										20,701
Release of restricted stock upon vesting (in Shares)		725,000
Balance as of at Dec. 31, 2013		$ 234,201	$ 82,938			$ 6,260				$ 323,399
Balance as of (in Shares) at Dec. 31, 2013		38,291,000								38,291