Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative related liabilities		$ (1)	$ (12)
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
Derivative related liabilities		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			(485)
Derivative related liabilities		(1)	(12)
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
Derivative related liabilities		0	0
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Netting	[1]	(17)	(15)
Netting	[1]	53	332
Recurring [Member] | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Netting	[1]	(17)	(15)
Netting	[1]	53	332
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] | 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		17	15
Total assets		17	15
Due to affiliates carried at fair value		0	(485)
Derivative related liabilities before netting		(54)	(344)
Financial and Nonfinancial Liabilities, Fair Value Disclosure		(307)	(2,146)
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		17	15
Derivative related liabilities before netting		(54)	(344)
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] | 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		(253)	(1,317)
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			(485)
Derivative related liabilities		(1)	(12)
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		0	(485)
Derivative related liabilities		(1)	(12)
Financial and Nonfinancial Liabilities, Fair Value Disclosure		(254)	(1,814)
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		17	15
Derivative related liabilities		(54)	(344)
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		(17)	(15)
Derivative related liabilities		53	332
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		$ (253)	$ (1,317)

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