Future Minimum Lease Payments and Debt Maturities (Detail) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Debt Credit Facilities And Lease Commitments [Abstract]
2017		$ 129
2018		108
2019		85
2020		67
2021		58
Thereafter		216
Total obligations and commitments		663
Total debt and lease obligations		663
2017		3
2018		3
2019		3
2020		297
2021		403
Thereafter		2,085
Total obligations and commitments		2,794
Discounts, premiums, and adjustments relating to hedging instruments		(12)
Total debt and lease obligations	[1]	$ 2,782	$ 4,732

[1] Book values include any discounts, premiums and adjustments related to hedging instruments.