Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative related liabilities		$ (57)	$ (82)
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Due to affiliates carried at fair value		0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Due to affiliates carried at fair value		(496)	(512)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Due to affiliates carried at fair value		0	0
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Netting	[1]	(135)	(291)
Netting	[1]	626	504
Recurring [Member] | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Netting	[1]	(135)	(291)
Netting	[1]	626	504
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Total assets		0	0
Due to affiliates carried at fair value		0	0
Derivative related liabilities before netting		0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure		0	0
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Derivative related liabilities before netting		0	0
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Derivative related liabilities before netting		0	0
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Derivative related liabilities before netting		0	0
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		135	291
Total assets		135	291
Due to affiliates carried at fair value		(496)	(512)
Derivative related liabilities before netting		(683)	(586)
Financial and Nonfinancial Liabilities, Fair Value Disclosure		(4,436)	(7,860)
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		24	144
Derivative related liabilities before netting		(304)	(453)
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		111	147
Derivative related liabilities before netting		(379)	(133)
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Derivative related liabilities before netting		0	0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Total assets		0	0
Due to affiliates carried at fair value		0	0
Derivative related liabilities before netting		0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure		0	0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Derivative related liabilities before netting		0	0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Derivative related liabilities before netting		0	0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets before netting		0	0
Derivative related liabilities before netting		0	0
Long-term Debt Carried at Fair Value [Member] | Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long term debt carried at fair value		0	0
Long-term Debt Carried at Fair Value [Member] | Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long term debt carried at fair value		(3,257)	(6,762)
Long-term Debt Carried at Fair Value [Member] | Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long term debt carried at fair value		0	0
Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Due to affiliates carried at fair value		(496)	(512)
Estimated Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets		0	0
Total assets		0	0
Due to affiliates carried at fair value		(496)	(512)
Derivative related liabilities		(57)	(82)
Financial and Nonfinancial Liabilities, Fair Value Disclosure		(3,810)	(7,356)
Estimated Fair Value [Member] | Recurring [Member] | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets		24	144
Derivative related liabilities		(304)	(453)
Estimated Fair Value [Member] | Recurring [Member] | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets		111	147
Derivative related liabilities		(379)	(133)
Estimated Fair Value [Member] | Recurring [Member] | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets		(135)	(291)
Derivative related liabilities		626	504
Estimated Fair Value [Member] | Long-term Debt Carried at Fair Value [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long term debt carried at fair value		$ (3,257)	$ (6,762)

[1] Represents counterparty and swap collateral netting which allow the offsetting of amounts relating to certain contracts when certain conditions are met.