Fair Value Measurements Fair Value Measurements - Summary of Fair Value Real Estate and Assets Held for Sale and Impairment Charges of Financial Assets and Liabilities (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	$ 52	$ 138
Real Estate | Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	310	299
Real Estate | Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	0	0
Real Estate | Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	7	31
Real Estate | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	$ 303	268
Right Of Use Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value		3
Right Of Use Assets | Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value		22
Right Of Use Assets | Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value		0
Right Of Use Assets | Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value		0
Right Of Use Assets | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value		$ 22
Measurement Input, Revenue Multiple | Valuation Technique, Discounted Cash Flow | Hotels Encumbered With Ground Lease | Minimum | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate investment, measurement input	2.0	2.0
Measurement Input, Revenue Multiple | Valuation Technique, Discounted Cash Flow | Hotels Encumbered With Ground Lease | Maximum | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate investment, measurement input	3.0	3.0