UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Agency revenues		$ 2,607	$ 2,567	$ 4,556	$ 4,680
Merchant revenues		959	710	1,562	1,236
Advertising and other revenues		284	260	569	549
Total revenues		3,850	3,537	6,687	6,465
Operating expenses:
Performance marketing		1,192	1,142	2,222	2,248
Brand marketing		175	124	338	225
Sales and other expenses		248	203	463	369
Personnel, including stock-based compensation of $79, $75, $153 and $146, respectively		619	522	1,120	1,021
General and administrative		180	159	371	322
Information technology		70	59	135	119
Depreciation and amortization		119	107	235	210
Total operating expenses		2,603	2,316	4,884	4,514
Operating income		1,247	1,221	1,803	1,951
Other income (expense):
Interest income		34	46	69	93
Interest expense		(68)	(65)	(134)	(135)
Net unrealized gains on marketable equity securities		17	21	468	76
Foreign currency transactions and other		(23)	(13)	(31)	(22)
Total other (expense) income		(40)	(11)	372	12
Earnings before income taxes		1,207	1,210	2,175	1,963
Income tax expense		228	232	431	378
Net income	[1]	$ 979	$ 978	$ 1,744	$ 1,585
Net income applicable to common stockholders per basic common share (in dollars per share)		$ 22.62	$ 20.34	$ 39.52	$ 32.87
Weighted-average number of basic common shares outstanding (in shares)		43,251	48,055	44,124	48,202
Net income applicable to common stockholders per diluted common share (in dollars per share)		$ 22.44	$ 20.13	$ 39.17	$ 32.42
Weighted-average number of diluted common shares outstanding (in shares)		43,601	48,550	44,514	48,877

[1] The Company reclassified from accumulated other comprehensive income net gains of $10 million ($9 million, net of tax) and $11 million ($10 million, net of tax) for the three and six months ended June 30, 2019, respectively, and a net loss of $1 million ($1 million, net of tax) for the six months ended June 30, 2018 from sales of investments in debt securities. The reclassified net gains (losses) are included in "Foreign currency transactions and other" in the Unaudited Consolidated Statements of Operations.