Investments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Realized gains (losses) on investments
Net realized investment (losses) gains	$ (107)	$ 39	$ 189	$ 188
Net impairment losses recognized in earnings	0	0	0	0
Indemnity
Realized gains (losses) on investments
Net realized investment (losses) gains	(1)	6	2	7
Indemnity \| Fixed maturities
Available-for-sale securities:
Gross realized gains	0	2	0	2
Gross realized losses	0	0	0	0
Net realized gains	0	2	0	2
Indemnity \| Equity securities
Available-for-sale securities:
Gross realized gains	0	2	0	3
Gross realized losses	0	0	0	0
Net realized gains	0	2	0	3
Indemnity \| Common stock
Trading securities:
Gross realized gains	0	1	1	2
Gross realized losses	0	0	0	0
Valuation adjustments	(1)	1	1	0
Net realized (losses) gains	(1)	2	2	2
Exchange
Realized gains (losses) on investments
Net realized investment (losses) gains	(106)	33	187	181
Net impairment losses recognized in earnings			0.1
Exchange \| Fixed maturities
Available-for-sale securities:
Gross realized gains	16	26	25	51
Gross realized losses	(3)	(5)	(6)	(17)
Net realized gains	13	21	19	34
Exchange \| Equity securities
Available-for-sale securities:
Gross realized gains	4	10	5	16
Gross realized losses	(2)	0	(2)	(1)
Net realized gains	2	10	3	15
Exchange \| Common stock
Trading securities:
Gross realized gains	44	71	85	127
Gross realized losses	(21)	(16)	(33)	(24)
Valuation adjustments	(144)	(53)	113	29
Net realized (losses) gains	$ (121)	$ 2	$ 165	$ 132

This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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