Commitments and Contingencies - Commitments (Detail) € in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) entity	Mar. 31, 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	10
North American Full-Service Property
Commitments and Contingencies Disclosure [Line Items]
Construction commitment	36
Information Technology Hardware, Software, Accounting, Finance, and Maintenance Services
Commitments and Contingencies Disclosure [Line Items]
Purchase commitments	131
Purchase commitments expected to be funded in 2016	70
Purchase commitments expected to be funded in 2017	49
Purchase commitments expected to be funded in 2018	9
Purchase commitments expected to be funded thereafter	3
Commitments
Commitments and Contingencies Disclosure [Line Items]
Investment commitments not expected to be funded	49
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	3
Investment commitments not expected to be funded	19
Limited Service | Equity Investment for Non Controlling Interest in Partnership Commitment | Upper Limit
Commitments and Contingencies Disclosure [Line Items]
Investment commitments	$ 22