Schedule III - Real Estate and Accumulated Depreciation - Change in Total Cost of Properties (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Real Estate And Accumulated Depreciation Disclosure [Abstract]
Balance at beginning of period	$ 11,566	$ 9,921	$ 10,249
Additions during period:
Acquisitions		2,220
Capital expenditures	66	248	192
Deductions during period:
Transfers to assets held for sale		(86)
Dispositions, including casualty losses and impairment loss on planned dispositions	(250)	(734)	(512)
Foreign exchange effect	(6)	(3)	(8)
Balance at end of period	$ 11,376	$ 11,566	$ 9,921