Derivative Financial Instruments (Summary of aggregate contractual or notional amounts and gross estimated fair values related to derivative financial instruments) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Summary of Derivative Instruments Without Hedge Designation
Contractual/notional amount	$ 66	$ 84
Estimated fair value asset
Estimated fair value (liability)		(3)
Credit default swap - purchased protection [Member]
Summary of Derivative Instruments Without Hedge Designation
Contractual/notional amount	20	20
Estimated fair value asset
Estimated fair value (liability)		(1)
Currency forwards [Member]
Summary of Derivative Instruments Without Hedge Designation
Contractual/notional amount	41	59
Estimated fair value asset
Estimated fair value (liability)		(2)
Equity warrants [Member]
Summary of Derivative Instruments Without Hedge Designation
Contractual/notional amount	5	5
Estimated fair value asset
Estimated fair value (liability)