Investments (Fixed Maturity and Equity Securities Available-For-Sale - Narrative) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of Certain Fixed Maturity Securities
Available-for-sale Securities, Debt Securities	$ 356,514	$ 374,266
Gross Unrealized OTTI Loss	277	361	724
Foreign corporate securities [Member]
Summary of Certain Fixed Maturity Securities
Available-for-sale Securities, Debt Securities	64,186	67,184
Net unrealized gains (losses)	3,893	5,654
Gross Unrealized OTTI Loss	(1)	(1)
Non-income producing fixed maturity securities [Member]
Summary of Certain Fixed Maturity Securities
Available-for-sale Securities, Debt Securities	69	85
Net unrealized gains (losses)	$ 22	$ 11

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details