Fair Value (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Level 3
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	$ 159	$ 231	$ 164	$ 206
Included in earnings	7	5	14	6
Included in other comprehensive income	0	(3)	(1)	1
Purchases	0	1	1	5
Sales	(4)	(13)	(14)	(20)
Transfers in and (out) of Level 3	0	(23)	(2)	0
Ending balance	162	198	162	198
Level 3 | Net realized investment gains losses
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Included in earnings		3	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	7	2	13	8
Indemnity
Fair value transfers due to changes in available market observable inputs
Transfers from level 1 to level 2	0	0	0	0
Transfers from level 2 to level 1	0	0	0	1
Transfers from level 2 to level 3	0	0	0	0
Transfers from level 3 to level 2	0	0	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	19	23	20	23
Included in earnings	1	0	2	1
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	(1)	(1)	(3)	(2)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	19	22	19	22
Indemnity | Level 3 | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	1	3	2	4
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	(1)	(1)	(2)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	1	2	1	2
Indemnity | Level 3 | Fixed maturities | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	1	3	2	4
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	(1)	(1)	(2)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	1	2	1	2
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	1	1
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	1	1	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	0	2	1	3
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	(1)	(1)	(2)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	0	1	0	1
Indemnity | Level 3 | Real estate | Limited partnerships
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	18	20	18	19
Included in earnings	1	0	2	1
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	(1)	0	(2)	0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	18	20	18	20
Exchange
Fair value transfers due to changes in available market observable inputs
Transfers from level 1 to level 2	11	0	14	5
Transfers from level 2 to level 1	0	0	0	44
Transfers from level 2 to level 3	0	0	0	18
Transfers from level 3 to level 2	0	23	2	18
Exchange | Fixed maturities
Fair value transfers due to changes in available market observable inputs
No. of securities transferred between Level 2 and Level 3				5
No. of securities transferred between Level 3 and Level 2		3	1	2
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		2	1
No. of securities transferred between Level 2 and Level 1				5
Exchange | Level 3
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	140	208	144	183
Included in earnings	6	5	12	5
Included in other comprehensive income	0	(3)	(1)	1
Purchases	0	1	1	5
Sales	(3)	(12)	(11)	(18)
Transfers in and (out) of Level 3	0	(23)	(2)	0
Ending balance	143	176	143	176
Exchange | Level 3 | Available-for-sale securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	27	89	31	59
Included in earnings	0	3	1	1
Included in other comprehensive income	0	(3)	(1)	1
Purchases	0	1	1	5
Sales	(1)	(11)	(4)	(10)
Transfers in and (out) of Level 3	0	(23)	(2)	0
Ending balance	26	56	26	56
Exchange | Level 3 | Trading securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	15	7	15	15
Included in earnings	0	0	0	(3)
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	(5)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	15	7	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	26	77	31	59
Included in earnings	0	1	1	1
Included in other comprehensive income	0	(2)	(1)	(2)
Purchases	0	1	0	1
Sales	(1)	(5)	(4)	(10)
Transfers in and (out) of Level 3	0	(23)	(2)	0
Ending balance	25	49	25	49
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	58	26	43
Included in earnings	0	0	0	0
Included in other comprehensive income	0	(1)	0	(1)
Purchases	0	1	0	1
Sales	(1)	(2)	(1)	(2)
Transfers in and (out) of Level 3	0	(23)	0	(8)
Ending balance	25	33	25	33
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		5		0
Included in earnings		0		0
Included in other comprehensive income		0		(1)
Purchases		0		0
Sales		(1)		(1)
Transfers in and (out) of Level 3		0		6
Ending balance		4		4
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	0	14	5	16
Included in earnings	0	1	1	1
Included in other comprehensive income	0	(1)	(1)	0
Purchases	0	0	0	0
Sales	0	(2)	(3)	(7)
Transfers in and (out) of Level 3	0	0	(2)	2
Ending balance	0	12	0	12
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	1	12	0	0
Included in earnings	0	2	0	0
Included in other comprehensive income	0	(1)	0	3
Purchases	0	0	1	4
Sales	0	(6)	0	0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	1	7	1	7
Exchange | Level 3 | Common stock | Trading securities
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Beginning balance	15	7	15	15
Included in earnings	0	0	0	(3)
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	(5)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	15	7	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	112	98	109
Included in earnings	6	2	11	7
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	(2)	(1)	(7)	(3)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	102	113	102	113
Fair value measurements on a recurring basis
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Ending balance	162		162
Fair value measurements on a recurring basis | Indemnity
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Ending balance	19		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		18
Fair value measurements on a recurring basis | Exchange
Roll forward of consolidated level 3 fair value measurements on a recurring basis
Ending balance	143		143
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	$ 102		$ 102