Commitments and Contingencies - Guarantees (Details) € in Millions, SGD in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016 SGD	Dec. 31, 2015	Mar. 31, 2016 USD ($)	Mar. 31, 2016 EUR (€)	Dec. 30, 2011 USD ($)	Sep. 09, 2005 EUR (€)
Primary Obligor
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			$ 222
Recorded Liability for Guarantees			60
Primary Obligor | Debt service
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			113
Recorded Liability for Guarantees			21
Primary Obligor | Debt service | New York City EDITION Hotel
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			315
Guarantor obligations, term	2 years
Guarantor obligations, extended term	3 years
Primary Obligor | Operating profit
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			100
Recorded Liability for Guarantees			38
Primary Obligor | Other
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			9
Recorded Liability for Guarantees			1
Primary Obligor | Not Yet In Effect Condition | Debt service
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			11
Primary Obligor | Not Yet In Effect Condition | Operating profit
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			44
Primary Obligor | Not Yet In Effect Condition | Other
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			1
Secondarily Liable
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			57
Secondarily Liable | MVW Spin-off
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			5
Guarantee obligations, carrying value			1
Secondarily Liable | MVW Spin-off | Expiration in 2022
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings | SGD	SGD 7
Secondarily Liable | Lease Obligations and Debt Securities Payable
Commitments and Contingencies Disclosure [Line Items]
Guarantee obligations, carrying value			3
Secondarily Liable | Property Lease Guarantee | Sunrise Senior Living Inc
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			41
Guarantee obligations, cash collateralized					$ 1
Collateral for continuing lease obligation contingency, future minimum annual payments due from 2014 until 2018					1
Secondarily Liable | Property Lease Guarantee | Sunrise Senior Living Inc | Key Bank | Letter of Credit
Commitments and Contingencies Disclosure [Line Items]
Letter of credit provided by Sunrise, amount available					$ 85
Letter of credit provided by Sunrise, amount available at period end			49
Secondarily Liable | Property Lease Guarantee | Renaissance Hotel Group N.V.
Commitments and Contingencies Disclosure [Line Items]
Guarantee obligations, cash collateralized			2	€ 2		€ 35
Annual rent payments, approximately			4
Remaining rent payments, approximately			18
Secondarily Liable | Debt Securities Payable
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			16
Secondarily Liable | Debt Securities Payable | Sunrise Senior Living Inc
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			3
Secondarily Liable | Debt Securities Payable | CNL Retirement Properties Inc
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			13
Secondarily Liable | Lease is Terminated by End of 2019 | Property Lease Guarantee | ExecuStay
Commitments and Contingencies Disclosure [Line Items]
Maximum Potential Amount of Future Fundings			6
Other noncurrent liabilities | Primary Obligor
Commitments and Contingencies Disclosure [Line Items]
Recorded Liability for Guarantees			$ 60
Minimum
Commitments and Contingencies Disclosure [Line Items]
Funding guarantees, minimum term		4 years
Maximum
Commitments and Contingencies Disclosure [Line Items]
Funding guarantees, minimum term		10 years