Derivative Financial Instruments - Summary of Aggregate Contractual or Notional Amounts and Gross Estimated Fair Values Related to Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
With hedge designation [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Contractual/Notional Amount	$ 300	$ 300
Estimated Fair Value, Asset	1
Estimated Fair Value, (Liability)	(4)	(6)
With hedge designation [Member] | Commodities, Forwards - short [Member]
Derivative [Line Items]
Contractual/Notional Amount	295	288
Estimated Fair Value, Asset	29	39
Estimated Fair Value, (Liability)	(3)	(3)
With hedge designation [Member] | Foreign exchange, Currency forwards - short [Member]
Derivative [Line Items]
Contractual/Notional Amount	222	144
Estimated Fair Value, Asset	1	4
Estimated Fair Value, (Liability)	(10)
Without hedge designation [Member] | Equity markets, Options - purchased [Member]
Derivative [Line Items]
Contractual/Notional Amount	1,010	255
Estimated Fair Value, Asset	37	19
Without hedge designation [Member] | Equity markets, Options - written [Member]
Derivative [Line Items]
Contractual/Notional Amount	606	374
Estimated Fair Value, (Liability)	(33)	(11)
Without hedge designation [Member] | Equity swaps and warrants - long [Member]
Derivative [Line Items]
Contractual/Notional Amount	18	14
Estimated Fair Value, Asset	13	6
Without hedge designation [Member] | Interest rate risk, Credit default swaps - purchased protection [Member]
Derivative [Line Items]
Contractual/Notional Amount	63	78
Estimated Fair Value, (Liability)	(2)	(2)
Without hedge designation [Member] | Interest rate risk, Credit default swaps - sold protection [Member]
Derivative [Line Items]
Contractual/Notional Amount	18	33
Estimated Fair Value, (Liability)		(2)
Without hedge designation [Member] | Foreign exchange, Currency forwards - long [Member]
Derivative [Line Items]
Contractual/Notional Amount	75	404
Estimated Fair Value, (Liability)		(2)
Without hedge designation [Member] | Foreign exchange, Currency forwards - short [Member]
Derivative [Line Items]
Contractual/Notional Amount	273	128
Estimated Fair Value, Asset	$ 6