CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Restricted Stock Units (RSUs)	Common Stock	Common Stock Restricted Stock 2012 Directors Plan	Common Stock Restricted Stock Units (RSUs)	Additional Paid-in Capital	Additional Paid-in Capital Restricted Stock Units (RSUs)	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive (Loss)/ Income
Balance, beginning of period (in shares) at Dec. 31, 2013			46,614,916
Balance, beginning of period at Dec. 31, 2013	$ 376,101		$ 46			$ 195,585		$ 190,986	$ (8,684)	$ (1,832)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued in connection with acquisition (Note 3)	(2,788)					(2,076)			(4,864)
Stock issued in connection with acquisition (Note 3) (in shares)			534,534
Forfeiture of stock issued in connection with acquisition						223			(223)
Forfeiture of stock issued in connection with acquisition (in shares)			(24,474)
Stock Issued or Granted During Period, Share-based Compensation [Abstract]
Proceeds from stock option exercises	10,598		$ 2			10,596
Proceeds from stock options exercises (in shares)			1,171,097
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures [Abstract]
Restricted stock issued (in shares)				7,738
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures [Abstract]
Stock-based compensation expense	21,397					21,397
Excess tax benefits	3,776					3,776
Prior periods retained earnings adjustment								(29)		29
Foreign currency translation adjustment	(20,251)									(20,251)
Net income	69,641							69,641
Balance, end of period (in shares) at Dec. 31, 2014			48,303,811
Balance, end of period at Dec. 31, 2014	464,050		$ 48			229,501		260,598	(4,043)	(22,054)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued in connection with acquisition (Note 3)	(5,081)					(1,118)			(3,963)
Stock issued in connection with acquisition (Note 3) (in shares)			435,462
Forfeiture of stock issued in connection with acquisition						13			(13)
Forfeiture of stock issued in connection with acquisition (in shares)			(1,482)
Stock Issued or Granted During Period, Share-based Compensation [Abstract]
Proceeds from stock option exercises	20,675		$ 1			20,674
Proceeds from stock options exercises (in shares)			1,405,826
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures [Abstract]
Restricted stock issued (in shares)				5,295	17,625
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures [Abstract]
Restricted stock issued		$ 574					$ 574
Stock-based compensation expense	43,120					43,120
Excess tax benefits	8,363					8,363
Foreign currency translation adjustment	(13,096)									(13,096)
Net income	84,456							84,456
Balance, end of period (in shares) at Dec. 31, 2015			50,166,537
Balance, end of period at Dec. 31, 2015	613,223		$ 49			303,363		345,054	(93)	(35,150)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Forfeiture of stock issued in connection with acquisition						84			(84)
Forfeiture of stock issued in connection with acquisition (in shares)			(9,228)
Stock Issued or Granted During Period, Share-based Compensation [Abstract]
Proceeds from stock option exercises	18,028		$ 1			18,027
Proceeds from stock options exercises (in shares)			895,804
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures [Abstract]
Restricted stock issued (in shares)				6,510
Restricted stock units issued, net of shares withheld for taxes (in shares)					38,064
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures [Abstract]
Restricted stock units vested, net of shares withheld for taxes	2,069						$ 2,069
Stock-based compensation expense	46,100					46,100
Excess tax benefits	5,264					5,264
Foreign currency translation adjustment	(2,538)									(2,538)
Net income	99,266							99,266
Balance, end of period (in shares) at Dec. 31, 2016			51,097,687
Balance, end of period at Dec. 31, 2016	$ 781,412		$ 50			$ 374,907		$ 444,320	$ (177)	$ (37,688)