CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net revenues	$ 1,190,202	$ 1,134,224	$ 1,059,429
Cost of net revenues	619,650	566,117	528,078
Restructuring	1,475	0	0
Gross profit	569,077	568,107	531,351
Operating expenses:
Technology and development	168,383	166,909	155,318
Sales and marketing	197,708	233,585	236,749
General and administrative	117,797	118,503	121,019
Capital lease termination	8,098	0	0
Restructuring	15,491	0	0
Total operating expenses	507,477	518,997	513,086
Income from operations	61,600	49,110	18,265
Interest expense	(27,836)	(23,023)	(20,998)
Interest and other income, net	1,481	501	744
Income (loss) before income taxes	35,245	26,588	(1,989)
(Provision for) benefit from income taxes	(5,160)	(10,682)	1,146
Net income (loss)	$ 30,085	$ 15,906	$ (843)
Net income (loss) per share:
Basic (in dollars per share)	$ 0.91	$ 0.47	$ (0.02)
Diluted (in dollars per share)	$ 0.88	$ 0.45	$ (0.02)
Weighted average shares:
Weighted-average common shares outstanding (in shares)	33,113	34,097	36,761
Weighted-average diluted shares outstanding (in shares)	34,106	35,190	36,761