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	Sep. 30, 2014	Dec. 31, 2013
Commodities, Forwards - Short [Member] | Discontinued Operations [Member]
Derivative [Line Items]
Contractual/Notional Amount		$ 180
Estimated Fair Value, Asset		4
Estimated Fair Value, (Liability)		(4)
Embedded Derivative on Funds Withheld Liability [Member]
Derivative [Line Items]
Contractual/Notional Amount	185
Estimated Fair Value, (Liability)	(1)
Interest Rate Risk, Interest Rate Swaps [Member] | Discontinued Operations [Member]
Derivative [Line Items]
Contractual/Notional Amount		300
Estimated Fair Value, (Liability)		(4)
With Hedge Designation [Member] | Foreign Exchange, Currency Forwards - Short [Member]
Derivative [Line Items]
Contractual/Notional Amount	133	114
Estimated Fair Value, Asset		2
Estimated Fair Value, (Liability)	(4)	(1)
Without Hedge Designation [Member] | Foreign Exchange, Currency Forwards - Short [Member]
Derivative [Line Items]
Contractual/Notional Amount	181	113
Estimated Fair Value, Asset	7
Without Hedge Designation [Member] | Equity Markets, Options - Purchased [Member]
Derivative [Line Items]
Contractual/Notional Amount	569	1,561
Estimated Fair Value, Asset	18	41
Without Hedge Designation [Member] | Equity Markets, Options - Written [Member]
Derivative [Line Items]
Contractual/Notional Amount	218	729
Estimated Fair Value, (Liability)	(18)	(23)
Without Hedge Designation [Member] | Equity Swaps and Warrants - Long [Member]
Derivative [Line Items]
Contractual/Notional Amount	12	17
Estimated Fair Value, Asset	4	9
Without Hedge Designation [Member] | Interest Rate Risk, Credit Default Swaps - Purchased Protection [Member]
Derivative [Line Items]
Contractual/Notional Amount		50
Estimated Fair Value, (Liability)		(3)
Without Hedge Designation [Member] | Interest Rate Risk, Credit Default Swaps - Sold Protection [Member]
Derivative [Line Items]
Contractual/Notional Amount		25
Without Hedge Designation [Member] | Foreign Exchange, Currency Forwards - Long [Member]
Derivative [Line Items]
Contractual/Notional Amount		55
Without Hedge Designation [Member] | Currency Options - Long [Member]
Derivative [Line Items]
Contractual/Notional Amount	625
Estimated Fair Value, Asset	13
Without Hedge Designation [Member] | Currency Options - Short [Member]
Derivative [Line Items]
Contractual/Notional Amount	$ 50