Fair Value (Details 2) (Level 3, USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	$ 75	$ 112	$ 78	$ 95
Included in earnings	0	1	1	2
Included in other comprehensive income	(1)	2	0	7
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		5
Transfers in and (out) of Level 3	0	(23)	0	(12)
Ending balance	74	92	74	92
Indemnity
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	4	13	4	11
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	1
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	(2)	0	(1)
Ending balance	4	11	4	11
Indemnity | Fixed maturities | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	4	11	4	10
Included in earnings	0	0	0	0
Included in other comprehensive income	0	1	0	1
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	(2)	0	(1)
Ending balance	4	10	4	10
Indemnity | Corporate debt securities | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance		2		2
Included in earnings		0		0
Included in other comprehensive income		0		0
Purchases, sales and adjustments		0		0
Transfers in and (out) of Level 3		0		0
Ending balance		2		2
Indemnity | Collateralized debt obligations (CDO) | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	4	9	4	8
Included in earnings	0	0	0	0
Included in other comprehensive income	0	1	0	1
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	(2)	0	(1)
Ending balance	4	8	4	8
Indemnity | Nonredeemable preferred stock | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance		2		1
Included in earnings		0		0
Included in other comprehensive income		(1)		0
Purchases, sales and adjustments		0		0
Transfers in and (out) of Level 3		0		0
Ending balance		1		1
Indemnity | Common stock | Trading securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	0	0	0	0
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	0	0	0	0
Indemnity | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	4	13	4	11
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	1
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	(2)	0	(1)
Ending balance	4	11	4	11
Indemnity | Trading securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	0	0	0	0
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	0	0	0	0
Exchange
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	71	99	74	84
Included in earnings	0	1	1	2
Included in other comprehensive income	(1)	2	0	6
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		5
Transfers in and (out) of Level 3	0	(21)	0	(11)
Ending balance	70	81	70	81
Exchange | Fixed maturities | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	50	84	55	71
Included in earnings	0	1	0	1
Included in other comprehensive income	0	3	0	6
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		5
Transfers in and (out) of Level 3	0	(21)	0	(11)
Ending balance	50	67	50	67
Exchange | States & political subdivisions | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	4		4
Included in earnings	0		0
Included in other comprehensive income	0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0		0
Ending balance	4		4
Exchange | Corporate debt securities | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	11	9	11	17
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	0	0	(8)
Ending balance	11	9	11	9
Exchange | Other debt securities | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	5	5	10	5
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		5
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	5	5	5	5
Exchange | Collateralized debt obligations (CDO) | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	30	70	30	49
Included in earnings	0	1	0	1
Included in other comprehensive income	0	3	0	6
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	(21)	0	(3)
Ending balance	30	53	30	53
Exchange | Nonredeemable preferred stock | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	8	5	7	4
Included in earnings	0	0	0	0
Included in other comprehensive income	(1)	(1)	0	0
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	7	4	7	4
Exchange | Available-for-sale securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	58	89	62	75
Included in earnings	0	1	0	1
Included in other comprehensive income	(1)	2	0	6
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		5
Transfers in and (out) of Level 3	0	(21)	0	(11)
Ending balance	57	71	57	71
Exchange | Trading securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	13	10	12	9
Included in earnings	0	0	1	1
Included in other comprehensive income	0	0	0	0
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	13	10	13	10
Exchange | Common stock | Trading securities
Roll forward of Level 3 fair value measurements on a recurring basis for consolidated available-for-sale and trading securities
Beginning balance	13	10	12	9
Included in earnings	0	0	1	1
Included in other comprehensive income	0	0	0	0
Purchases, sales and adjustments		0		0
Purchases	0		0
Sales	0		0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	$ 13	$ 10	$ 13	$ 10