Fair Value Measurement Fair Value Measurement - Schedule of Liabilities Measured at Fair Value on Recurring Basis Quantitative Information about Level 3 Fair Value Measurements (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative Liabilities, Gross Amount	$ 1,031	$ 1,438
Fair Value, Measurements, Recurring [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative Liabilities, Gross Amount	433	1,102
Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative Liabilities, Gross Amount	30	29
Fair Value, Measurements, Recurring [Member] | Level 3 | Derivative liabilities
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative Liabilities, Gross Amount	$ 30	$ 29
Fair Value, Measurements, Recurring [Member] | Level 3 | Derivative liabilities | Discounted cash flows | Minimum
Fair Value Inputs [Abstract]
Swap rates (percent)	2.00%	2.00%
Fair Value, Measurements, Recurring [Member] | Level 3 | Derivative liabilities | Discounted cash flows | Maximum
Fair Value Inputs [Abstract]
Swap rates (percent)	2.00%	2.00%
Fair Value, Measurements, Recurring [Member] | Level 3 | Derivative liabilities | Discounted cash flows | Weighted Average
Fair Value Inputs [Abstract]
Swap rates (percent)	2.00%	2.00%