Basis of Presentation - Effect of Adoption of ASU 2014-09 on Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES
Net income	$ 398	$ 371
Adjustments to reconcile to cash provided by operating activities:
Depreciation, amortization, and other	73	62
Share-based compensation	42	48
Income taxes	16	86
Liability for guest loyalty programs	325	69
Contract acquisition costs	(29)	(53)
Merger-related charges	(16)	(36)
Working capital changes	(185)	(135)
(Gain) loss on asset dispositions	(60)	1
Other	111	49
Net cash provided by (used in) operating activities	675	462
INVESTING ACTIVITIES
Capital expenditures	(64)	(48)
Dispositions	108	311
Loan advances	(12)	(28)
Loan collections	5	7
Contract acquisition costs		0
Other	12	1
Net cash provided by investing activities	49	243
FINANCING ACTIVITIES
Commercial paper/Credit facility, net	627	(26)
Issuance of long-term debt	0	1
Repayment of long-term debt	(13)	(4)
Issuance of Class A Common Stock	4	2
Dividends paid	(118)	(115)
Purchase of treasury stock	(815)	(582)
Share-based compensation withholding taxes	(95)	(99)
Net cash provided by (used in) financing activities	(410)	(823)
INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	314	(118)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of period	429	887
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of period	$ 743	769
As Previously Reported
OPERATING ACTIVITIES
Net income		365
Adjustments to reconcile to cash provided by operating activities:
Depreciation, amortization, and other		65
Share-based compensation		48
Income taxes		82
Liability for guest loyalty programs		60
Contract acquisition costs		0
Merger-related charges		(36)
Working capital changes		(108)
(Gain) loss on asset dispositions		1
Other		49
Net cash provided by (used in) operating activities		526
INVESTING ACTIVITIES
Capital expenditures		(48)
Dispositions		311
Loan advances		(28)
Loan collections		7
Contract acquisition costs		(54)
Other		(4)
Net cash provided by investing activities		184
FINANCING ACTIVITIES
Commercial paper/Credit facility, net		(33)
Issuance of long-term debt		1
Repayment of long-term debt		(4)
Issuance of Class A Common Stock		2
Dividends paid		(115)
Purchase of treasury stock		(582)
Share-based compensation withholding taxes		(99)
Net cash provided by (used in) financing activities		(830)
INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		(120)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of period		858
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of period		738
Adoption of ASU 2014-09 | Adjustment
OPERATING ACTIVITIES
Net income		6
Adjustments to reconcile to cash provided by operating activities:
Depreciation, amortization, and other		(3)
Share-based compensation		0
Income taxes		4
Liability for guest loyalty programs		9
Contract acquisition costs		(53)
Merger-related charges		0
Working capital changes		(28)
(Gain) loss on asset dispositions		0
Other		7
Net cash provided by (used in) operating activities		(58)
INVESTING ACTIVITIES
Capital expenditures		0
Dispositions		0
Loan advances		0
Loan collections		0
Contract acquisition costs		54
Other		4
Net cash provided by investing activities		58
FINANCING ACTIVITIES
Commercial paper/Credit facility, net		0
Issuance of long-term debt		0
Repayment of long-term debt		0
Issuance of Class A Common Stock		0
Dividends paid		0
Purchase of treasury stock		0
Share-based compensation withholding taxes		0
Net cash provided by (used in) financing activities		0
INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		0
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of period		0
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of period		0
Adoption of ASUs 2016-18 and 2016-15 | Adjustment
OPERATING ACTIVITIES
Net income		0
Adjustments to reconcile to cash provided by operating activities:
Depreciation, amortization, and other		0
Share-based compensation		0
Income taxes		0
Liability for guest loyalty programs		0
Contract acquisition costs		0
Merger-related charges		0
Working capital changes		1
(Gain) loss on asset dispositions		0
Other		(7)
Net cash provided by (used in) operating activities		(6)
INVESTING ACTIVITIES
Capital expenditures		0
Dispositions		0
Loan advances		0
Loan collections		0
Contract acquisition costs		0
Other		1
Net cash provided by investing activities		1
FINANCING ACTIVITIES
Commercial paper/Credit facility, net		7
Issuance of long-term debt		0
Repayment of long-term debt		0
Issuance of Class A Common Stock		0
Dividends paid		0
Purchase of treasury stock		0
Share-based compensation withholding taxes		0
Net cash provided by (used in) financing activities		7
INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		2
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of period		29
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of period		$ 31