Investments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Realized gains (losses) on investments
Net realized investment gains	$ 296	$ 149
Net impairment losses recognized in earnings	0	0
Indemnity
Realized gains (losses) on investments
Net realized investment gains	3	1
Indemnity \| Fixed maturities
Available-for-sale securities:
Gross realized gains	0	0
Gross realized losses	0	0
Net realized gains	0	0
Indemnity \| Equity securities
Available-for-sale securities:
Gross realized gains	0	1
Gross realized losses	0	0
Net realized gains	0	1
Indemnity \| Common stock
Trading securities:
Gross realized gains	1	1
Gross realized losses	0	0
Valuation adjustments	2	(1)
Net realized gains	3	0
Exchange
Realized gains (losses) on investments
Net realized investment gains	293	148
Net impairment losses recognized in earnings	0.1
Exchange \| Fixed maturities
Available-for-sale securities:
Gross realized gains	9	25
Gross realized losses	(3)	(12)
Net realized gains	6	13
Exchange \| Equity securities
Available-for-sale securities:
Gross realized gains	1	6
Gross realized losses	0	(1)
Net realized gains	1	5
Exchange \| Common stock
Trading securities:
Gross realized gains	41	56
Gross realized losses	(12)	(8)
Valuation adjustments	257	82
Net realized gains	$ 286	$ 130

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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