Condensed Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Net revenue	$ 363,661	$ 228,207	$ 688,366	$ 416,663
Costs and expenses:
Cost of revenue (exclusive of depreciation and amortization shown separately below)	49,264	30,367	91,648	55,500
Sales and marketing	122,276	75,740	231,693	141,624
Product development	95,608	60,080	176,280	107,173
General and administrative	56,225	30,974	99,009	55,828
Depreciation and amortization	32,193	17,548	57,999	32,430
Total costs and expenses	355,566	214,709	656,629	392,555
Income from operations	8,095	13,498	31,737	24,108
Other expense, net	(252)	(668)	(560)	(444)
Income before income taxes	7,843	12,830	31,177	23,664
Provision for income taxes	4,109	10,019	4,827	15,864
Net income	$ 3,734	$ 2,811	$ 26,350	$ 7,800
Net income per share of common stock:
Basic (in dollars per share)	$ 0.03	$ 0.03	$ 0.24	$ 0.08
Diluted (in dollars per share)	$ 0.03	$ 0.03	$ 0.23	$ 0.07
Weighted-average shares used to compute net income per share:
Basic (in shares)	111,214	104,185	110,334	103,198
Diluted (in shares)	116,627	112,317	116,017	111,813