Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 4,520,992	$ 3,700,856
Cost of revenues	2,870,614	2,300,579
Marketing	616,578	536,777
Technology and development	372,764	282,310
General and administrative	201,952	134,612
Operating income	459,084	446,578
Other income (expense):
Interest expense	(135,529)	(81,219)
Interest and other income (expense)	76,104	(65,743)
Income before income taxes	399,659	299,616
Provision for income taxes	55,607	9,492
Net income	$ 344,052	$ 290,124
Earnings per share:
Basic (in dollars per share)	$ 0.79	$ 0.67
Diluted (in dollars per share)	$ 0.76	$ 0.64
Weighted-average common shares outstanding:
Basic (in shares)	436,947	434,174
Diluted (in shares)	451,922	450,359