Investments (Net Investment Gains Losses - Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment portfolio gains (losses)	$ 0	$ 95
Non-investment portfolio gains (losses)	7	(25)
Gains (losses) from foreign currency transactions	58	58
Investments sold [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment portfolio gains (losses)	0	102
Impairments [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment portfolio gains (losses)	0	(7)
Non-investment portfolio gain (loss) related to disposal of certain closed blocks of business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-investment portfolio gains (losses)	$ 30	$ 0