Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock Including Additional Paid in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2012	$ 194,079	$ 60,040	$ 4,175	$ 258,294
Balance (in Shares) at Dec. 31, 2012	35,673
Net income		22,898		22,898
Other comprehensive income (loss)			2,085	2,085
Exercise of stock options	$ 37,877			$ 37,877
Exercise of stock options (in Shares)	2,446			2,446
Repurchase of common shares	$ (20,615)			$ (20,615)
Repurchase of common shares (in Shares)	(664)
Shares issued under the employee stock purchase plan	$ 2,145			2,145
Shares issued under the employee stock purchase plan (in Shares)	111
Stock-based compensation expense	$ 20,715			20,715
Release of restricted stock (in Shares)	725
Balance at Dec. 31, 2013	$ 234,201	82,938	6,260	323,399
Balance (in Shares) at Dec. 31, 2013	38,291
Net income		35,495		35,495
Other comprehensive income (loss)			(449)	(449)
Dividends and dividend equivalents declared		(18,319)		(18,319)
Exercise of stock options	$ 11,941			$ 11,941
Exercise of stock options (in Shares)	742			742
Repurchase of common shares	$ (41,198)			$ (41,198)
Repurchase of common shares (in Shares)	(1,051)
Shares issued under the employee stock purchase plan	$ 2,078			2,078
Shares issued under the employee stock purchase plan (in Shares)	78
Stock-based compensation expense	$ 33,459			33,459
Tax benefits from equity awards	$ 19			19
Release of restricted stock (in Shares)	772
Balance at Dec. 31, 2014	$ 240,500	100,114	5,811	$ 346,425
Balance (in Shares) at Dec. 31, 2014	38,832			38,832
Net income		35,172		$ 35,172
Other comprehensive income (loss)			(4,345)	(4,345)
Dividends and dividend equivalents declared		(33,999)		(33,999)
Exercise of stock options	$ 7,744			$ 7,744
Exercise of stock options (in Shares)	498			498
Repurchase of common shares	$ (32,286)			$ (32,286)
Repurchase of common shares (in Shares)	(645)
Shares issued under the employee stock purchase plan	$ 2,227			2,227
Shares issued under the employee stock purchase plan (in Shares)	56
Stock-based compensation expense	$ 41,650			41,650
Tax benefits from equity awards	$ 5,928			5,928
Release of restricted stock (in Shares)	948
Balance at Dec. 31, 2015	$ 265,763	$ 101,287	$ 1,466	$ 368,516
Balance (in Shares) at Dec. 31, 2015	39,689			39,689