Investments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available for Sale Securities
Amortized cost	$ 71,915	$ 73,379
Gross unrealized gains	5,632	4,404
Gross unrealized losses	(530)	(1,670)
Fair value	77,017	76,113
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	4,387	5,966
Gross unrealized gains	326	349
Fair value	4,713	6,315
Municipal
Schedule of Available for Sale Securities
Amortized cost	12,139	13,634
Gross unrealized gains	1,038	863
Gross unrealized losses	(108)	(256)
Fair value	13,069	14,241
Corporate
Schedule of Available for Sale Securities
Amortized cost	44,943	41,217
Gross unrealized gains	3,721	2,743
Gross unrealized losses	(127)	(379)
Fair value	48,537	43,581
Foreign government
Schedule of Available for Sale Securities
Amortized cost	2,290	1,866
Gross unrealized gains	228	216
Gross unrealized losses	(1)	(1)
Fair value	2,517	2,081
ABS
Schedule of Available for Sale Securities
Amortized cost	3,623	4,180
Gross unrealized gains	108	73
Gross unrealized losses	(107)	(287)
Fair value	3,624	3,966
RMBS
Schedule of Available for Sale Securities
Amortized cost	3,000	4,532
Gross unrealized gains	142	110
Gross unrealized losses	(110)	(521)
Fair value	3,032	4,121
CMBS
Schedule of Available for Sale Securities
Amortized cost	1,510	1,962
Gross unrealized gains	65	48
Gross unrealized losses	(77)	(226)
Fair value	1,498	1,784
Redeemable preferred stock
Schedule of Available for Sale Securities
Amortized cost	23	22
Gross unrealized gains	4	2
Fair value	$ 27	$ 24

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

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Number 115

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+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details