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	Dec. 31, 2011	Dec. 31, 2010
Summary of Derivative Instruments Without Hedge Designation
Contractual/notional amount	$ 46	$ 49
Estimated fair value asset	1	1
Estimated fair value (liability)	(1)	(2)
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)	(2)
Credit default swap - sold protection [Member]
Summary of Derivative Instruments Without Hedge Designation
Contractual/notional amount		8
Estimated fair value asset		1
Estimated fair value (liability)
Currency forwards [Member]
Summary of Derivative Instruments Without Hedge Designation
Contractual/notional amount	22	18
Estimated fair value asset	1
Estimated fair value (liability)
Equity warrants [Member]
Summary of Derivative Instruments Without Hedge Designation
Contractual/notional amount	4	3
Estimated fair value asset
Estimated fair value (liability)