Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt carried at fair value	$ (9,700)		$ (13,700)
Derivative related liabilities	(22)		(26)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0
Due to affiliates carried at fair value	0
Long-term debt carried at fair value	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0
Due to affiliates carried at fair value	(514)
Long-term debt carried at fair value	(9,725)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0
Due to affiliates carried at fair value	0
Long-term debt carried at fair value	0
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Available-for-sale securities	80		188
Total assets	80		188
Due to affiliates carried at fair value	(514)		(447)
Long-term debt carried at fair value	(9,725)		(13,664)
Derivative related liabilities	(22)		(26)
Total liabilities	(10,261)		(14,137)
Recurring [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			80
Recurring [Member] | U.S. government sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			1
Recurring [Member] | U.S. corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			57
Recurring [Member] | Corporate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			26
Recurring [Member] | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			10
Recurring [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	80		13
Recurring [Member] | Accrued Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			1
Recurring [Member] | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	524		973
Derivative related liabilities	(1,585)		(1,762)
Recurring [Member] | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	1,159		1,503
Derivative related liabilities	(45)		(163)
Recurring [Member] | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	(1,683)		(2,476)
Derivative related liabilities	(1,608)		1,902
Recurring [Member] | Foreign exchange forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative related liabilities			(3)
Recurring [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Available-for-sale securities	80		103
Total assets	80		103
Due to affiliates carried at fair value	0		0
Long-term debt carried at fair value	0		0
Derivative related liabilities	0		0
Total liabilities	0		0
Recurring [Member] | Level 1 | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			80
Recurring [Member] | Level 1 | U.S. government sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 1 | U.S. corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 1 | Corporate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 1 | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			10
Recurring [Member] | Level 1 | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	80		13
Recurring [Member] | Level 1 | Accrued Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 1 | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Derivative related liabilities	0		0
Recurring [Member] | Level 1 | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Derivative related liabilities	0		0
Recurring [Member] | Level 1 | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Derivative related liabilities	0		0
Recurring [Member] | Level 1 | Foreign exchange forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative related liabilities			0
Recurring [Member] | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	1,683		2,476
Available-for-sale securities	0		85
Total assets	1,683		2,561
Due to affiliates carried at fair value	(514)		(447)
Long-term debt carried at fair value	(9,725)		(13,664)
Derivative related liabilities	(1,630)		(1,928)
Total liabilities	(11,869)		(16,039)
Recurring [Member] | Level 2 | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 2 | U.S. government sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			1
Recurring [Member] | Level 2 | U.S. corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			57
Recurring [Member] | Level 2 | Corporate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			26
Recurring [Member] | Level 2 | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 2 | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring [Member] | Level 2 | Accrued Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			1
Recurring [Member] | Level 2 | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	524		973
Derivative related liabilities	(1,585)		(1,762)
Recurring [Member] | Level 2 | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	1,159		1,503
Derivative related liabilities	(45)		(163)
Recurring [Member] | Level 2 | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Derivative related liabilities	0		0
Recurring [Member] | Level 2 | Foreign exchange forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative related liabilities			(3)
Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Available-for-sale securities	0		0
Total assets	0		0
Due to affiliates carried at fair value	0		0
Long-term debt carried at fair value	0		0
Derivative related liabilities	0		0
Total liabilities	0		0
Recurring [Member] | Level 3 | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 3 | U.S. government sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 3 | U.S. corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 3 | Corporate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 3 | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 3 | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring [Member] | Level 3 | Accrued Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0
Recurring [Member] | Level 3 | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Derivative related liabilities	0		0
Recurring [Member] | Level 3 | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Derivative related liabilities	0		0
Recurring [Member] | Level 3 | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0		0
Derivative related liabilities	0		0
Recurring [Member] | Level 3 | Foreign exchange forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative related liabilities			0
Recurring [Member] | Netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	(1,683)	[1]	(2,476)	[1]
Available-for-sale securities	0	[1]	0	[1]
Total assets	(1,683)	[1]	(2,476)	[1]
Due to affiliates carried at fair value	0	[1]	0	[1]
Long-term debt carried at fair value	0	[1]	0	[1]
Derivative related liabilities	1,608	[1]	1,902	[1]
Total liabilities	1,608	[1]	1,902	[1]
Recurring [Member] | Netting [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0	[1]
Recurring [Member] | Netting [Member] | U.S. government sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0	[1]
Recurring [Member] | Netting [Member] | U.S. corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0	[1]
Recurring [Member] | Netting [Member] | Corporate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0	[1]
Recurring [Member] | Netting [Member] | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0	[1]
Recurring [Member] | Netting [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0	[1]
Recurring [Member] | Netting [Member] | Accrued Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities			0	[1]
Recurring [Member] | Netting [Member] | Interest rate swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0	[1]	0	[1]
Derivative related liabilities	0	[1]	0	[1]
Recurring [Member] | Netting [Member] | Currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	0	[1]	0	[1]
Derivative related liabilities	0	[1]	0	[1]
Recurring [Member] | Netting [Member] | Derivative netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial assets	(1,683)	[1]	(2,476)	[1]
Derivative related liabilities	(1,608)	[1]	1,902	[1]
Recurring [Member] | Netting [Member] | Foreign exchange forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative related liabilities			$ 0	[1]

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