CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Agency revenues	$ 3,142,815	$ 2,339,253	$ 1,380,603
Merchant revenues	2,104,752	2,004,432	1,691,640
Other revenues	13,389	11,925	12,662
Total revenues	5,260,956	4,355,610	3,084,905
Cost of revenues	1,177,275	1,275,730	1,175,934
Gross profit	4,083,681	3,079,880	1,908,971
Operating expenses:
Advertising - Online	1,273,637	919,214	552,140
Advertising - Offline	35,492	35,470	35,714
Sales and marketing	195,934	162,690	116,303
Personnel, including stock-based compensation of $71,565, $65,724, and $68,200, respectively	466,828	352,295	270,071
General and administrative	173,171	123,652	81,185
Information technology	43,685	33,813	20,998
Depreciation and amortization	65,141	53,824	45,763
Total operating expenses	2,253,888	1,680,958	1,122,174
Operating income	1,829,793	1,398,922	786,797
Other income (expense):
Interest income	3,860	8,119	3,857
Interest expense	(62,064)	(31,721)	(29,944)
Foreign currency transactions and other	(9,720)	(7,526)	(14,427)
Total other income (expense)	(67,924)	(31,128)	(40,514)
Earnings before income taxes	1,761,869	1,367,794	746,283
Income Tax Expense	337,832	308,663	218,141
Net income	1,424,037	1,059,131	528,142
Less: net income attributable to noncontrolling interests	4,471	2,760	601
Net income applicable to common stockholders	$ 1,419,566	$ 1,056,371	$ 527,541
Net income applicable to common stockholders per basic common share (in dollars per share)	$ 28.48	$ 21.27	$ 11.00
Weighted average number of basic common shares outstanding (in shares)	49,840	49,654	47,955
Net income applicable to common stockholders per diluted common share (in dollars per share)	$ 27.66	$ 20.63	$ 10.35
Weighted average number of diluted common shares outstanding (in shares)	51,326	51,211	50,988