Schedule III - Real Estate and Accumulated Depreciation - Change in Accumulated Depreciation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real Estate And Accumulated Depreciation Disclosure [Abstract]
Balance at beginning of period	$ 1,832	$ 1,639	$ 1,372
Additions during period:
Depreciation expense	280	292	279
Deductions during period:
Transfers to assets held for sale	(15)
Dispositions, including casualty losses	(85)	(95)	(3)
Foreign exchange effect	(8)	(4)	(9)
Balance at end of period	$ 2,004	$ 1,832	$ 1,639