CONDENSED CONSOLIDATED STATEMENT OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net revenues	$ 3,857	$ 3,136	$ 7,542	$ 6,111
Operating expenses:
Transaction expense	1,362	1,064	2,637	2,051
Transaction and loan losses	334	308	639	608
Customer support and operations	357	335	708	652
Sales and marketing	313	284	598	522
Product development	255	232	513	446
General and administrative	368	282	707	547
Depreciation and amortization	180	201	365	384
Restructuring and other charges	116	0	269	40
Total operating expenses	3,285	2,706	6,436	5,250
Operating income	572	430	1,106	861
Other income (expense), net	37	17	51	24
Income before income taxes	609	447	1,157	885
Income tax expense	83	36	120	90
Net income	$ 526	$ 411	$ 1,037	$ 795
Net income per share:
Basic (in usd per share)	$ 0.44	$ 0.34	$ 0.87	$ 0.66
Diluted (in usd per share)	$ 0.44	$ 0.34	$ 0.86	$ 0.65
Weighted average shares:
Basic (in shares)	1,187	1,202	1,190	1,203
Diluted (in shares)	1,202	1,215	1,209	1,216