CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Agency revenues	$ 6,527,898	$ 5,845,802	$ 4,410,689
Merchant revenues	2,082,973	2,186,054	2,211,474
Advertising and other revenues	613,116	410,115	171,143
Total revenues	9,223,987	8,441,971	6,793,306
Cost of revenues	632,180	857,841	1,077,420
Gross profit	8,591,807	7,584,130	5,715,886
Operating expenses:
Advertising — Online	2,797,237	2,360,221	1,798,645
Advertising — Offline	214,685	231,309	127,459
Sales and marketing	353,221	310,910	235,817
Personnel, including stock-based compensation of $247,395, $186,425 and $140,526, respectively	1,166,226	950,191	698,692
General and administrative	415,420	352,869	252,994
Information technology	113,617	97,498	71,890
Depreciation and amortization	272,494	207,820	117,975
Total operating expenses	5,332,900	4,510,818	3,303,472
Operating income	3,258,907	3,073,312	2,412,414
Other income (expense):
Interest income	55,729	13,933	4,167
Interest expense	(160,229)	(88,353)	(83,289)
Foreign currency transactions and other	(26,087)	(9,444)	(36,755)
Total other income (expense)	(130,587)	(83,864)	(115,877)
Earnings before income taxes	3,128,320	2,989,448	2,296,537
Income tax expense	576,960	567,695	403,739
Net income	2,551,360	2,421,753	1,892,798
Less: net income attributable to noncontrolling interests	0	0	135
Net income applicable to common stockholders	$ 2,551,360	$ 2,421,753	$ 1,892,663
Net income applicable to common stockholders per basic common share	$ 50.09	$ 46.30	$ 37.17
Weighted average number of basic common shares outstanding	50,940	52,301	50,924
Net income applicable to common stockholders per diluted common share	$ 49.45	$ 45.67	$ 36.11
Weighted average number of diluted common shares outstanding	51,593	53,023	52,413