Summarization of Bases Used to Measure Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current maturities of long-term debt and lease obligations	[1]	$ 3	$ 810
Long-term debt and lease obligations	[1]	2,779	3,922
Approximate fair values
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		31	21
Total assets		31	21
Short-term debt			1,775
Current maturities of long-term debt and lease obligations		3	818
Long-term debt and lease obligations		2,756	4,077
Total liabilities		2,759	6,670
Fair Value, Inputs, Level 2 | Approximate fair values
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments			2
Total assets			2
Short-term debt			1,775
Current maturities of long-term debt and lease obligations		3	818
Long-term debt and lease obligations		2,756	4,077
Total liabilities		2,759	6,670
Fair Value, Inputs, Level 3 | Approximate fair values
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments		31	19
Total assets		$ 31	$ 19

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