Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2009	$ 311,945	$ 294	$ 325,207	$ 129,559	$ (141,250)	$ (1,865)
Beginning Balance, Shares at Dec. 31, 2009		29,362			7,028
Issuance of common stock under stock plans, including tax benefit, Shares		1,138
Issuance of common stock under stock plans, including tax benefit	27,744	11	27,733
Stock-based compensation expense	4,874		4,874
Purchase of common stock, Shares					660
Purchase of common stock	(21,345)				(21,345)
Dividend paid on common shares	(68,414)			(68,414)
Capital contributed by seller of acquired business	203		203
Net income	20,507			20,507
Unrealized loss on marketable investments, net of tax	(925)					(925)
Cumulative translation adjustment	(2,682)					(2,682)
Ending Balance at Dec. 31, 2010	271,907	305	358,017	81,652	(162,595)	(5,472)
Ending Balance, Shares at Dec. 31, 2010		30,500			7,688
Issuance of common stock under stock plans, including tax benefit, Shares		462
Issuance of common stock under stock plans, including tax benefit	11,937	5	11,932
Stock-based compensation expense	3,642		3,642
Purchase of common stock, Shares					527
Purchase of common stock	(18,405)				(18,405)
Net income	23,010			23,010
Unrealized loss on marketable investments, net of tax	(21)					(21)
Cumulative translation adjustment	(1,335)					(1,335)
Ending Balance at Dec. 31, 2011	290,735	310	373,591	104,662	(181,000)	(6,828)
Ending Balance, Shares at Dec. 31, 2011		30,962			8,215
Issuance of common stock under stock plans, including tax benefit, Shares		489
Issuance of common stock under stock plans, including tax benefit	10,379	5	10,374
Stock-based compensation expense	5,397		5,397
Purchase of common stock, Shares					943
Purchase of common stock	(29,843)				(29,843)
Dividend paid on common shares	(12,588)			(12,588)
Net income	25,574			25,574
Unrealized loss on marketable investments, net of tax	(3)					(3)
Cumulative translation adjustment	7,419					7,419
Ending Balance at Dec. 31, 2012	$ 297,070	$ 315	$ 389,362	$ 117,648	$ (210,843)	$ 588
Ending Balance, Shares at Dec. 31, 2012		31,451			9,158