Other Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Other Liabilities [Line Items]
Asset Retirement Obligation, Accretion Expense		$ 15	$ 14	$ 13
Other Liabilities, non-current	[1]	2,516	3,110		$ 2,458	$ 2,411	$ 2,369	$ 3,074	$ 3,014	$ 2,946
Estimated Future Undiscounted Cash Flows Expected To Be Paid Relating To Asset Retirement Obligations		1,000
Amortization of Below Market Tenant Lease		65	69	37
Accrued Payroll and Other Compensation		174	157
Above Market Leases [Member]
Other Liabilities [Line Items]
Amortization of Above Market Leases			18	$ 19
Deferred Revenue [Domain]
Other Liabilities [Line Items]
Other Liabilities, non-current		1,814	1,618
deferred ground lease payable [Member]
Other Liabilities [Line Items]
Other Liabilities, non-current	[2]	0	603
Above Market Leases [Member]
Other Liabilities [Line Items]
Other Liabilities, non-current	[2]	0	181
deferred credits [Member]
Other Liabilities [Line Items]
Other Liabilities, non-current		434	499
asset retirement obligations [Member]
Other Liabilities [Line Items]
Other Liabilities, non-current		227	192
Deferred Tax Liability, noncurrent [Member]
Other Liabilities [Line Items]
Other Liabilities, non-current		8	7
Other Liabilities [Member]
Other Liabilities [Line Items]
Other Liabilities, non-current		33	$ 10
Amortization of Below-Market Leases, 2020 [Domain]
Other Liabilities [Line Items]
Expected amortization of below-market tenant leases by year		57
Amortization of Below-Market Leases, 2021 [Domain]
Other Liabilities [Line Items]
Expected amortization of below-market tenant leases by year		53
Amortization of Below-Market Leases, 2022 [Domain]
Other Liabilities [Line Items]
Expected amortization of below-market tenant leases by year		49
Amortization of Below-Market Leases, 2023 [Member]
Other Liabilities [Line Items]
Expected amortization of below-market tenant leases by year		45
Amortization of Below-Market Leases, 2024 [Member]
Other Liabilities [Line Items]
Expected amortization of below-market tenant leases by year		$ 41

[1] See "Recently Adopted Accounting Pronouncements" in note 3 to the consolidated financial statements for a discussion of the recently adopted new lease standard.

[2] See "Recently Adopted Accounting Pronouncements" in note 3 for a discussion of the recently adopted new lease standard, including with respect to deferred ground lease payable and above-market leases previously classified as other long-term liabilities.