UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Agency revenues		$ 1,949	$ 2,113
Merchant revenues		603	526
Advertising and other revenues		285	289
Total revenues		2,837	2,928
Operating expenses:
Performance marketing		1,030	1,106
Brand marketing		163	101
Sales and other expenses		215	166
Personnel, including stock-based compensation of $74 and $71, respectively		501	499
General and administrative		191	163
Information technology		65	60
Depreciation and amortization		116	103
Total operating expenses		2,281	2,198
Operating income		556	730
Other income (expense):
Interest income		35	47
Interest expense		(66)	(70)
Net unrealized gains on marketable equity securities		451	55
Foreign currency transactions and other		(8)	(9)
Total other income		412	23
Earnings before income taxes		968	753
Income tax expense		203	146
Net income	[1]	$ 765	$ 607
Net income applicable to common stockholders per basic common share (in dollars per share)		$ 17.01	$ 12.56
Weighted-average number of basic common shares outstanding (in shares)		45,007	48,349
Net income applicable to common stockholders per diluted common share (in dollars per share)		$ 16.85	$ 12.34
Weighted-average number of diluted common shares outstanding (in shares)		45,436	49,205

[1] The Company realized net gains of $1 million for the three months ended March 31, 2019 from sales of investments in debt securities.