Fair Value of Financial Instruments Fair Value of Financial Instruments - Schedule of Liabilities Measured at Fair Value on Recurring Basis Quantitative Information about Level 3 Fair Value Measurements (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative liabilities	$ 369	$ 710
Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative liabilities	39	38
Recurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative liabilities	369	710
Recurring | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative liabilities	39	38
Recurring | Level 3 | Derivative liabilities
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative liabilities	$ 39	$ 38
Recurring | Level 3 | Derivative liabilities | Minimum | Discounted cash flows
Fair Value Inputs [Abstract]
Swap rates (percent)	3.00%	3.00%
Recurring | Level 3 | Derivative liabilities | Maximum | Discounted cash flows
Fair Value Inputs [Abstract]
Swap rates (percent)	3.00%	4.00%
Recurring | Level 3 | Derivative liabilities | Weighted Average | Discounted cash flows
Fair Value Inputs [Abstract]
Swap rates (percent)	3.00%	4.00%