Contingencies - Guarantees (Details) € in Millions, SGD in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 EUR (€)	Dec. 31, 2015 SGD	Sep. 09, 2005 EUR (€)
New York City EDITION Hotel
Commitments and Contingencies Disclosure [Line Items]
Loan commitment, put option agreement, obligation to acquire property, amount	$ 315
Loan commitment, put option agreement, obligation to acquire property, term	2 years
Loan commitment, put option agreement, obligation to acquire property, extended term	3 years
Property Lease Guarantee | ExecuStay
Commitments and Contingencies Disclosure [Line Items]
Liability for guarantees		$ 1
Lease Obligations and Debt Securities Payable
Commitments and Contingencies Disclosure [Line Items]
Liability for guarantees		3
Primary Obligor
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		228
Liability for guarantees		67
Primary Obligor | Guarantee, Indebtedness of Others
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		113
Liability for guarantees		23
Primary Obligor | Guarantee, Operating Profit
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		103
Liability for guarantees		43
Primary Obligor | Guarantee type, other
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		12
Liability for guarantees		1
Primary Obligor | Not Yet In Effect Condition | Guarantee, Indebtedness of Others
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		11
Primary Obligor | Not Yet In Effect Condition | Guarantee, Operating Profit
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		42
Primary Obligor | Not Yet In Effect Condition | Other Guarantees
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		1
Primary Obligor | Other Current Liabilities
Commitments and Contingencies Disclosure [Line Items]
Liability for guarantees		4
Primary Obligor | Other Long Term Liabilities
Commitments and Contingencies Disclosure [Line Items]
Liability for guarantees		63
Secondarily Liable
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		62
Secondarily Liable | MVW Spin-off
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		5		SGD 7
Liability for guarantees		1
Secondarily Liable | Property Lease Guarantee | Sunrise Senior Living Inc
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		46
Cash collateral in the event funding is required		1
Collateral for continuing lease obligation contingency, future minimum annual payments due		1
Secondarily Liable | Property Lease Guarantee | Sunrise Senior Living Inc | Letter of Credit | Key Bank
Commitments and Contingencies Disclosure [Line Items]
Letter of credit provided by Sunrise, amount available		85
Line of credit facility provided by third party, current borrowing capacity for period		55
Secondarily Liable | Property Lease Guarantee | Renaissance Hotel Group N.V.
Commitments and Contingencies Disclosure [Line Items]
Annual rent payments, approximately		4
Remaining rent payments, approximately		19
Guarantee obligations, cash collateralized		3	€ 2		€ 35
Secondarily Liable | Debt Securities Payable
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		16
Secondarily Liable | Debt Securities Payable | Sunrise Senior Living Inc
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		3
Secondarily Liable | Debt Securities Payable | CNL Retirement Properties Inc
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		13
Secondarily Liable | Lease is Terminated After End of 2013 | Property Lease Guarantee | ExecuStay
Commitments and Contingencies Disclosure [Line Items]
Guarantor obligations, maximum exposure, undiscounted		$ 6
Lower Limit
Commitments and Contingencies Disclosure [Line Items]
Guarantee obligations, term		4 years
Upper Limit
Commitments and Contingencies Disclosure [Line Items]
Guarantee obligations, term		10 years