Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance ($) at Dec. 31, 2010	$ 438,863	$ 127	$ 296,571	$ (12,416)	$ 154,581
Balance (shares) at Dec. 31, 2010		126,950,468
Issuance of common stock
Exercise of stock options and release of stock awards (including excess tax benefit) ($)	55,863	5	55,858
Exercise of stock options and release of stock awards (including excess tax benefit) (shares)		4,913,504
Stock-based activity and issuance of common stock to board of directors ($)	779	0	779
Stock-based activity and issuance of common stock to board of directors (shares)		23,102
Issuance of shares from Employee Stock Purchase Plans ($)	1,050	0	1,050
Issuance of shares from Employee Stock Purchase Plans (shares)		25,755
Issuance of shares in acquisitions ($)	0
Total issuance of common stock ($)	57,692	5	57,687
Total issuance of common stock (shares)		4,962,361
Share-based compensation expense	28,773		28,773
Net income	76,411				76,411
Cumulative translation adjustment	(2,316)			(2,316)
Balance ($) at Dec. 31, 2011	599,423	132	383,031	(14,732)	230,992
Balance (shares) at Dec. 31, 2011		131,912,829
Issuance of common stock
Exercise of stock options and release of stock awards (including excess tax benefit) ($)	82,314	6	82,308
Exercise of stock options and release of stock awards (including excess tax benefit) (shares)		5,689,164
Stock-based activity and issuance of common stock to board of directors ($)	542	0	542
Stock-based activity and issuance of common stock to board of directors (shares)		12,862
Issuance of shares from Employee Stock Purchase Plans ($)	5,016	0	5,016
Issuance of shares from Employee Stock Purchase Plans (shares)		137,104
Issuance of shares in acquisitions ($)	2,745	0	2,745
Issuance of shares in acquisitions (shares)		45,896
Total issuance of common stock ($)	90,617	6	90,611
Total issuance of common stock (shares)		5,885,026
Share-based compensation expense	41,546		41,546
Net income	105,418				105,418
Cumulative translation adjustment	6,643			6,643
Balance ($) at Dec. 31, 2012	843,647	138	515,188	(8,089)	336,410
Balance (shares) at Dec. 31, 2012		137,797,855
Issuance of common stock
Exercise of stock options and release of stock awards (including excess tax benefit) ($)	51,187	3	51,184
Exercise of stock options and release of stock awards (including excess tax benefit) (shares)		3,027,169
Issuance of shares from Employee Stock Purchase Plans ($)	6,186	0	6,186
Issuance of shares from Employee Stock Purchase Plans (shares)		190,235
Issuance of shares in acquisitions ($)	4,457	0	4,457
Issuance of shares in acquisitions (shares)		108,645
Total issuance of common stock ($)	61,830	3	61,827
Total issuance of common stock (shares)		3,326,049
Share-based compensation expense	59,645		59,645
Net income	86,737				86,737
Cumulative translation adjustment	3,553			3,553
Balance ($) at Dec. 31, 2013	$ 1,055,412	$ 141	$ 636,660	$ (4,536)	$ 423,147
Balance (shares) at Dec. 31, 2013		141,123,904