Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenues	$ 8,830,669	$ 6,779,511	$ 5,504,656
Cost of revenues	6,029,901	4,591,476	3,752,760
Marketing	991,078	824,092	607,186
Technology and development	852,098	650,788	472,321
General and administrative	577,799	407,329	269,741
Operating income	379,793	305,826	402,648
Other income (expense):
Interest expense	(150,114)	(132,716)	(50,219)
Interest and other income (expense)	30,828	(31,225)	(3,060)
Income before income taxes	260,507	141,885	349,369
Provision for income taxes	73,829	19,244	82,570
Net income	$ 186,678	$ 122,641	$ 266,799
Earnings per share:
Basic (in USD per share)	$ 0.44	$ 0.29	$ 0.63
Diluted (in USD per share)	$ 0.43	$ 0.28	$ 0.62
Weighted-average common shares outstanding:
Basic (in shares)	428,822	425,889	420,544
Diluted (in shares)	438,652	436,456	431,894