Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenues	$ 3,700,856	$ 2,636,635
Cost of revenues	2,196,075	1,657,024
Marketing	479,222	271,270
Technology and development	300,730	257,108
General and administrative	278,251	194,291
Operating income	446,578	256,942
Other income (expense):
Interest expense	(81,219)	(46,742)
Interest and other income (expense)	(65,743)	13,592
Income before income taxes	299,616	223,792
Provision for income taxes	9,492	45,570
Net income	$ 290,124	$ 178,222
Earnings per share:
Basic (in dollars per share)	$ 0.67	$ 0.41
Diluted (in dollars per share)	$ 0.64	$ 0.40
Weighted-average common shares outstanding:
Basic (in shares)	434,174	430,600
Diluted (in shares)	450,359	445,458