Fair Value (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Level 3
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	$ 164	$ 206
Included in earnings	7	3
Included in other comprehensive income	(1)	5
Purchases	1	4
Sales	(10)	(13)
Transfers in and (out) of Level 3	(2)	26
Ending balance	159	231
Level 3 | Net realized investment gains losses
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Included in earnings	1	(2)
Level 3 | Equity in earnings of limited partnerships
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Included in earnings	6	5
Indemnity
Fair value transfers due to changes in available market observable inputs
Transfers from level 1 to level 2	0	0
Transfers from level 2 to level 1	0	1
Transfers from level 2 to level 3	0	0
Transfers from level 3 to level 2	0	0
Indemnity | Nonredeemable preferred stock
Fair value transfers due to changes in available market observable inputs
No. of securities transferred between Level 2 and Level 1		1
Indemnity | Level 3
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	20	23
Included in earnings	1	1
Included in other comprehensive income	0	0
Purchases	0	0
Sales	(2)	(1)
Transfers in and (out) of Level 3	0	0
Ending balance	19	23
Indemnity | Level 3 | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	2	4
Included in earnings	0	0
Included in other comprehensive income	0	0
Purchases	0	0
Sales	(1)	(1)
Transfers in and (out) of Level 3	0	0
Ending balance	1	3
Indemnity | Level 3 | Fixed maturities | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	2	4
Included in earnings	0	0
Included in other comprehensive income	0	0
Purchases	0	0
Sales	(1)	(1)
Transfers in and (out) of Level 3	0	0
Ending balance	1	3
Indemnity | Level 3 | Corporate debt securities | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	1	1
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	1	1
Indemnity | Level 3 | Collateralized debt obligations | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	1	3
Included in earnings	0	0
Included in other comprehensive income	0	0
Purchases	0	0
Sales	(1)	(1)
Transfers in and (out) of Level 3	0	0
Ending balance	0	2
Indemnity | Level 3 | Real estate | Limited partnerships
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	18	19
Included in earnings	1	1
Included in other comprehensive income	0	0
Purchases	0	0
Sales	(1)	0
Transfers in and (out) of Level 3	0	0
Ending balance	18	20
Exchange
Fair value transfers due to changes in available market observable inputs
Transfers from level 1 to level 2	3	6
Transfers from level 2 to level 1	0	51
Transfers from level 2 to level 3	0	39
Transfers from level 3 to level 2	2	13
Exchange | Fixed maturities
Fair value transfers due to changes in available market observable inputs
No. of securities transferred between Level 2 and Level 3		7
No. of securities transferred between Level 3 and Level 2	1	1
Exchange | Nonredeemable preferred stock
Fair value transfers due to changes in available market observable inputs
No. of securities transferred between Level 1 and Level 2	1	1
No. of securities transferred between Level 2 and Level 1		5
No. of securities transferred between Level 2 and Level 3		1
Exchange | Level 3
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	144	183
Included in earnings	6	2
Included in other comprehensive income	(1)	5
Purchases	1	4
Sales	(8)	(12)
Transfers in and (out) of Level 3	(2)	26
Ending balance	140	208
Exchange | Level 3 | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	31	59
Included in earnings	1	1
Included in other comprehensive income	(1)	5
Purchases	1	4
Sales	(3)	(6)
Transfers in and (out) of Level 3	(2)	26
Ending balance	27	89
Exchange | Level 3 | Trading securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	15	15
Included in earnings	0	(3)
Included in other comprehensive income	0	0
Purchases	0	0
Sales	0	(5)
Transfers in and (out) of Level 3	0	0
Ending balance	15	7
Exchange | Level 3 | Fixed maturities | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	31	59
Included in earnings	1	1
Included in other comprehensive income	(1)	2
Purchases	0	0
Sales	(3)	(6)
Transfers in and (out) of Level 3	(2)	21
Ending balance	26	77
Exchange | Level 3 | Corporate debt securities | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	26	43
Included in earnings	0	0
Included in other comprehensive income	0	1
Purchases	0	0
Sales	0	(1)
Transfers in and (out) of Level 3	0	15
Ending balance	26	58
Exchange | Level 3 | Commercial mortgage-backed securities | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance		0
Included in earnings		0
Included in other comprehensive income		0
Purchases		0
Sales		0
Transfers in and (out) of Level 3		5
Ending balance		5
Exchange | Level 3 | Collateralized debt obligations | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	5	16
Included in earnings	1	1
Included in other comprehensive income	(1)	1
Purchases	0	0
Sales	(3)	(5)
Transfers in and (out) of Level 3	(2)	1
Ending balance	0	14
Exchange | Level 3 | Nonredeemable preferred stock | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	0	0
Included in earnings	0	0
Included in other comprehensive income	0	3
Purchases	1	4
Sales	0	0
Transfers in and (out) of Level 3	0	5
Ending balance	1	12
Exchange | Level 3 | Common stock | Trading securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	15	15
Included in earnings	0	(3)
Included in other comprehensive income	0	0
Purchases	0	0
Sales	0	(5)
Transfers in and (out) of Level 3	0	0
Ending balance	15	7
Exchange | Level 3 | Real estate | Limited partnerships
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	98	109
Included in earnings	5	4
Included in other comprehensive income	0	0
Purchases	0	0
Sales	(5)	(1)
Transfers in and (out) of Level 3	0	0
Ending balance	98	112
Fair value measurements on a recurring basis
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Ending balance	159
Fair value measurements on a recurring basis | Indemnity
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Ending balance	19
Fair value measurements on a recurring basis | Indemnity | Real estate
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Ending balance	18
Fair value measurements on a recurring basis | Exchange
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Ending balance	140
Fair value measurements on a recurring basis | Exchange | Real estate
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Ending balance	$ 98