CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Net revenues	$ 473,270	$ 307,707	$ 246,432
Cost of net revenues	219,542	134,491	111,648
Gross profit	253,728	173,216	134,784
Operating expenses:
Technology and development	65,675	48,393	46,003
Sales and marketing	113,952	59,284	44,870
General and administrative	58,710	40,764	35,201
Total operating expenses	238,337	148,441	126,074
Income from operations	15,391	24,775	8,710
Interest expense	(64)	(42)	(157)
Interest and other income, net	35	482	814
Income before income taxes	15,362	25,215	9,367
Provision for income taxes	(1,314)	(8,088)	(3,514)
Net income	14,048	17,127	5,853
Net income per share:
Basic (in dollars per share)	$ 0.43	$ 0.63	$ 0.23
Diluted (in dollars per share)	$ 0.40	$ 0.59	$ 0.22
Weighted average shares:
Basic (in shares)	32,788	27,025	25,420
Diluted (in shares)	35,007	29,249	26,810
Stock-based compensation is allocated as follows (Notes 2 and 6):
Cost of net revenues	2,138	508	416
Technology and development	8,201	3,069	3,340
Sales and marketing	11,350	3,923	3,577
General and administrative	$ 12,181	$ 8,866	$ 6,940