Investments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	$ 25,822	$ 27,427
Gross unrealized gain	2,486	1,747
Gross unrealized loss	(191)	(418)
Fair Value	28,117	28,756
U.S. government and agencies
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	668	678
Gross unrealized gain	102	90
Gross unrealized loss	0	(2)
Fair Value	770	766
Municipal
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	3,156	3,135
Gross unrealized gain	520	231
Gross unrealized loss	(14)	(62)
Fair Value	3,662	3,304
Corporate
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	19,465	20,397
Gross unrealized gain	1,670	1,214
Gross unrealized loss	(150)	(295)
Fair Value	20,985	21,316
Foreign government
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	654	715
Gross unrealized gain	81	83
Gross unrealized loss	0	(6)
Fair Value	735	792
ABS
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	773	1,011
Gross unrealized gain	13	30
Gross unrealized loss	(21)	(34)
Fair Value	765	1,007
RMBS
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	554	752
Gross unrealized gain	55	50
Gross unrealized loss	(4)	(12)
Fair Value	605	790
CMBS
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	538	724
Gross unrealized gain	43	47
Gross unrealized loss	(2)	(7)
Fair Value	579	764
Redeemable preferred stock
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	14	15
Gross unrealized gain	2	2
Gross unrealized loss	0	0
Fair Value	$ 16	$ 17

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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

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