Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenues	$ 4,923,116	$ 3,907,270	$ 9,444,108	$ 7,608,126
Cost of revenues	3,005,657	2,402,431	5,876,271	4,703,010
Marketing	603,150	592,007	1,219,728	1,128,784
Technology and development	383,233	299,095	755,997	581,405
General and administrative	224,657	151,524	426,609	286,136
Operating income	706,419	462,213	1,165,503	908,791
Other income (expense):
Interest expense	(152,033)	(101,605)	(287,562)	(182,824)
Interest and other income (expense)	(53,470)	68,028	22,634	2,285
Income before income taxes	500,916	428,636	900,575	728,252
Provision for income taxes	230,266	44,287	285,873	53,779
Net income	$ 270,650	$ 384,349	$ 614,702	$ 674,473
Earnings per share:
Basic (in dollars per share)	$ 0.62	$ 0.88	$ 1.41	$ 1.55
Diluted (in dollars per share)	$ 0.60	$ 0.85	$ 1.36	$ 1.50
Weighted-average common shares outstanding:
Basic (in shares)	437,587	435,097	437,271	434,638
Diluted (in shares)	452,195	451,552	452,063	450,958