CONSOLIDATED STATEMENTS OF CHANGES IN REDEEMABLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Jointech	Great Fridays	Common Stock	Common Stock Empathy Lab, LLC	Common Stock Netsoft	Common Stock Jointech	Common Stock GGA	Common Stock Great Fridays	Additional Paid-in Capital	Additional Paid-in Capital Empathy Lab, LLC	Additional Paid-in Capital Netsoft	Additional Paid-in Capital Jointech	Additional Paid-in Capital GGA	Additional Paid-in Capital Great Fridays	Retained Earnings	Treasury Stock	Treasury Stock Empathy Lab, LLC	Treasury Stock Netsoft	Treasury Stock Jointech	Treasury Stock GGA	Treasury Stock Great Fridays	Accumulated Other Comprehensive Income
Balance, beginning of period (in shares) at Dec. 31, 2012				44,442,494
Balance, beginning of period at Dec. 31, 2012	$ 286,280			$ 44						$ 166,962						$ 128,992	$ (8,697)						$ (1,021)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued (in shares)				14,041
Stock issued in connection with acquisition (in shares)					1,483
Stock issued in connection with acquisition											$ (13)							$ 13
Stock-based compensation expense	$ 13,150									13,150
Proceeds from stock options exercises (in shares)	2,156,898			2,156,898
Proceeds from stock options exercises	$ 9,287			$ 2						9,285
Excess tax benefits	6,201									6,201
Currency translation adjustment	(811)																						(811)
Net income	61,994															61,994
Balance, end of period (in shares) at Dec. 31, 2013				46,614,916
Balance, end 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 shares)				7,738
Awards forfeited/cancelled					(24,474)
Forfeiture of stock issued in connection with acquisition											$ (223)							$ 223
Stock issued in connection with acquisition (in shares)						2,289	179,104	262,277	90,864
Stock issued in connection with acquisition		$ 2,788										$ (21)	$ 1,158	$ (2,386)	$ (827)				$ 21	$ 1,630	$ 2,386	$ 827
Stock-based compensation expense	$ 21,397									21,397
Proceeds from stock options exercises (in shares)	1,171,097			1,171,097
Proceeds from stock options exercises	$ 10,598			$ 2						10,596
Excess tax benefits	3,776									3,776
Prior periods retained earning adjustment																(29)							29
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 shares)				5,295
Awards forfeited/cancelled						(1,482)
Forfeiture of stock issued in connection with acquisition												13							13
Issuance of restricted stock (in shares)				17,625
Restricted stock units vested	574									574
Stock issued in connection with acquisition (in shares)						25,503	166,114	233,753	10,092
Stock issued in connection with acquisition		$ 5,000	$ 81									$ (232)	$ 3,488	$ (2,127)	$ (11)				$ 232	$ 1,512	$ 2,127	$ 92
Stock-based compensation expense	$ 43,120									43,120
Proceeds from stock options exercises (in shares)	1,405,826			1,405,826
Proceeds from stock options exercises	$ 20,675			$ 1						20,674
Excess tax benefits	8,363									8,363
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)