Change in Accumulated Depreciation and Amortization of Real Estate Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Real Estate And Accumulated Depreciation Other Required Disclosures [Abstract]
Beginning Balance	$ 6,364	$ 6,373	$ 6,272
Depreciation and amortization	541	535	546
Dispositions and other	(96)	(544)	(344)
Depreciation on assets held for sale			(101)
Ending Balance	$ 6,809	$ 6,364	$ 6,373