Change in Accumulated Depreciation and Amortization of Real Estate Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Real Estate And Accumulated Depreciation Other Required Disclosures [Abstract]
Beginning Balance	$ 5,666	$ 5,283	$ 4,962
Depreciation and amortization	572	558	540
Dispositions and other	(159)	(148)	(219)
Depreciation on assets held for sale	(130)	(27)
Ending Balance	$ 5,949	$ 5,666	$ 5,283