Commitments and Contingencies - Commitments (Detail) € in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($) entity	Jun. 30, 2016 EUR (€) entity
Investment in Other Joint Venture Commitment
Commitments and Contingencies Disclosure [Line Items]
Acquisition interests in joint ventures | entity	2	2
Contingent acquisition period	5 years
Deposits in conjunction with contingent obligation to acquire the interest in joint ventures	$ 20	€ 15
Deposits in conjunction with contingent obligation to acquire the interest in joint ventures, remaining amount	13	€ 11
Real Estate Investment | Upper Limit
Commitments and Contingencies Disclosure [Line Items]
Investment commitments expected to be funded in current year	3
North American Full-Service Property
Commitments and Contingencies Disclosure [Line Items]
Loan commitment	52
Loan commitment expected to be funded in 2016	5
Loan commitment expected to be funded in 2017	38
Loan commitment expected to be funded thereafter	9
Information Technology Hardware, Software, Accounting, Finance, and Maintenance Services
Commitments and Contingencies Disclosure [Line Items]
Purchase commitments	120
Purchase commitments expected to be funded in 2016	54
Purchase commitments expected to be funded in 2017	51
Purchase commitments expected to be funded in 2018	11
Purchase commitments expected to be funded thereafter	4
Commitments
Commitments and Contingencies Disclosure [Line Items]
Investment commitments not expected to be funded	40
Full Service and Limited Service | Equity Investment for Non Controlling Interest in Partnership Commitment
Commitments and Contingencies Disclosure [Line Items]
Investment commitments expected to be funded in 2016	1
Investment commitments not expected to be funded	7
Full Service and Limited Service | Equity Investment for Non Controlling Interest in Partnership Commitment | Upper Limit
Commitments and Contingencies Disclosure [Line Items]
Investment commitments	8
Limited Service | Equity Investment for Non Controlling Interest in Partnership Commitment
Commitments and Contingencies Disclosure [Line Items]
Investment commitments expected to be funded in 2016	2
Investment commitments not expected to be funded	20
Limited Service | Equity Investment for Non Controlling Interest in Partnership Commitment | Upper Limit
Commitments and Contingencies Disclosure [Line Items]
Investment commitments	$ 22