Business Segments - Segment Revenues (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 5,305	$ 5,409	$ 10,317	$ 10,418
Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	5,227	5,091	10,100	9,932
Unallocated corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	78	318	217	486
North American Full-Service | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	3,403	3,356	6,708	6,655
North American Limited-Service | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	901	860	1,670	1,600
Asia Pacific | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	310	268	580	543
Other International | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	613	607	1,142	1,134
Fee revenues
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	999	951	1,894	1,796
Contract investment amortization	(15)	(13)	(29)	(31)
Revenues	984	938	1,865	1,765
Fee revenues | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	867	833	1,642	1,567
Contract investment amortization	(15)	(13)	(29)	(31)
Revenues	852	820	1,613	1,536
Fee revenues | North American Full-Service | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	349	345	665	644
Contract investment amortization	(8)	(7)	(16)	(18)
Revenues	341	338	649	626
Fee revenues | North American Limited-Service | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	264	250	476	446
Contract investment amortization	(3)	(3)	(6)	(6)
Revenues	261	247	470	440
Fee revenues | Asia Pacific | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	112	110	230	227
Contract investment amortization	(1)	(1)	(1)	(1)
Revenues	111	109	229	226
Fee revenues | Other International | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	142	128	271	250
Contract investment amortization	(3)	(2)	(6)	(6)
Revenues	139	126	265	244
Owned, leased, and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	418	423	793	829
Owned, leased, and other | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	403	403	766	796
Owned, leased, and other | North American Full-Service | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	147	140	294	295
Owned, leased, and other | North American Limited-Service | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	38	37	69	70
Owned, leased, and other | Asia Pacific | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	50	48	91	95
Owned, leased, and other | Other International | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	168	178	312	336
Reimbursements
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	3,903	4,048	7,659	7,824
Reimbursements | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	3,972	3,868	7,721	7,600
Reimbursements | North American Full-Service | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	2,915	2,878	5,765	5,734
Reimbursements | North American Limited-Service | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	602	576	1,131	1,090
Reimbursements | Asia Pacific | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	149	111	260	222
Reimbursements | Other International | Total segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 306	$ 303	$ 565	$ 554