Investments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Realized gains (losses) on investments
Net realized investment gains (losses)	$ 61	$ (107)	$ 310	$ 189
Other-than-temporary impairments on investments
Net impairment losses recognized in earnings	1.0	0	1.0	0
Indemnity
Realized gains (losses) on investments
Net realized investment gains (losses)	0	(1)	0	2
Other-than-temporary impairments on investments
Net impairment losses recognized in earnings	0.1	0	0.1	0
Portion recognized in other comprehensive income	0	0	0	0
Indemnity \| Fixed maturities
Available-for-sale securities:
Gross realized gains	0	0	0	0
Gross realized losses	0	0	0	0
Net realized gains	0	0	0	0
Indemnity \| Equity securities
Available-for-sale securities:
Gross realized gains	0	0	0	0
Gross realized losses	0	0	0	0
Net realized gains	0	0	0	0
Indemnity \| Common stock
Trading securities:
Gross realized gains	0	0	0	1
Gross realized losses	0	0	0	0
Increases (decreases) in fair value(1)	0	(1)	0	1
Net realized (losses) gains	0	(1)	0	2
Exchange
Realized gains (losses) on investments
Net realized investment gains (losses)	61	(106)	310	187
Other-than-temporary impairments on investments
Net impairment losses recognized in earnings	1.0	0	1.0	0.1
Portion recognized in other comprehensive income	0	0	0	0
Exchange \| Fixed maturities
Available-for-sale securities:
Gross realized gains	7	16	22	25
Gross realized losses	(3)	(3)	(5)	(6)
Net realized gains	4	13	17	19
Exchange \| Equity securities
Available-for-sale securities:
Gross realized gains	2	4	4	5
Gross realized losses	0	(2)	0	(2)
Net realized gains	2	2	4	3
Exchange \| Common stock
Trading securities:
Gross realized gains	54	44	156	85
Gross realized losses	(3)	(21)	(15)	(33)
Increases (decreases) in fair value(1)	4	(144)	148	113
Net realized (losses) gains	$ 55	$ (121)	$ 289	$ 165

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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Before tax amount of other than temporary impairment (OTTI) on a debt security, categorized as available-for-sale, recognized in other comprehensive income (loss).

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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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