Financial Data Resulting from Transactions with Related Parties, Income Statement Data (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Base management fees	[1]									$ 698	$ 672	$ 621
Incentive management fees	[1]									319	302	256
Cost reimbursements	[1]									11,630	11,055	10,291
Total revenue		$ 3,706	$ 3,578	$ 3,689	$ 3,513	$ 3,559	$ 3,460	$ 3,484	$ 3,293	14,486	13,796	12,784
Reimbursed costs	[1]									(11,630)	(11,055)	(10,291)
Depreciation, amortization, and other	[1]									(139)	(148)	(127)
General, administrative, and other	[1]									(634)	(659)	(649)
Related Party Transactions
Related Party Transaction [Line Items]
Base management fees										15	17	17
Incentive management fees										3	6	1
Owned, leased, and other revenue										1	1	1
Cost reimbursements										197	226	236
Total revenue										216	250	255
Reimbursed costs										(197)	(226)	(236)
Depreciation, amortization, and other										(2)	(2)	(2)
General, administrative, and other										(1)	(2)	(3)
Interest income										5	5	4
Equity in earnings (losses)										$ 16	$ 6	$ (5)

[1] See Footnote No. 17, “Related Party Transactions,” to our Consolidated Financial Statements for disclosure of related party amounts.