Fair Value (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Level 3
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	$ 170	$ 238	$ 206	$ 190
Included in earnings	4	4	18	16
Included in other comprehensive income	1	1	0	3
Purchases	0	1	9	2
Sales	(11)	(15)	(61)	(28)
Transfers in and (out) of Level 3	0	(23)	(8)	23
Ending balance	164	206	164	206
Level 3 | Net realized investment gains (losses)
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Included in earnings	2	1	6	3
Level 3 | Equity in earnings of limited partnerships
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Included in earnings	2	3	12	13
Indemnity
Fair value transfers due to changes in available market observable inputs
Transfers from level 1 to level 2	0	4	0	5
Transfers from level 2 to level 1	0	0	1	0
Transfers from level 2 to level 3	0	0	0	1
Transfers from level 3 to level 2	0	0	0	0
Indemnity | Fixed maturities
Fair value transfers due to changes in available market observable inputs
No. of securities transferred between Level 2 and Level 3				1
Indemnity | Nonredeemable preferred stock
Fair value transfers due to changes in available market observable inputs
No. of securities transferred between Level 1 and Level 2		2		2
No. of securities transferred between Level 2 and Level 1			1
Indemnity | Level 3
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	21	22	23	21
Included in earnings	0	1	1	2
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	(1)	0	(4)	(1)
Transfers in and (out) of Level 3	0	0	0	1
Ending balance	20	23	20	23
Indemnity | Level 3 | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	2	4	4	4
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	(2)	(1)
Transfers in and (out) of Level 3	0	0	0	1
Ending balance	2	4	2	4
Indemnity | Level 3 | Fixed maturities | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	2	4	4	4
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	(2)	(1)
Transfers in and (out) of Level 3	0	0	0	1
Ending balance	2	4	2	4
Indemnity | Level 3 | Corporate debt securities | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	1	1	1	0
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	1
Ending balance	1	1	1	1
Indemnity | Level 3 | Collateralized debt obligations | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	1	3	3	4
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	(2)	(1)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	1	3	1	3
Indemnity | Level 3 | Real estate | Limited partnerships
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	19	18	19	17
Included in earnings	0	1	1	2
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	19	18	19
Exchange
Fair value transfers due to changes in available market observable inputs
Transfers from level 1 to level 2	0	69	6	79
Transfers from level 2 to level 1	0	0	51	12
Transfers from level 2 to level 3	0	12	39	33
Transfers from level 3 to level 2	0	35	47	11
Exchange | Fixed maturities
Fair value transfers due to changes in available market observable inputs
No. of securities transferred between Level 1 and Level 2		7		8
No. of securities transferred between Level 2 and Level 3		1	7	5
No. of securities transferred between Level 3 and Level 2		3	6	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		10	1	8
No. of securities transferred between Level 2 and Level 1			5	1
No. of securities transferred between Level 2 and Level 3			1
No. of securities transferred between Level 3 and Level 2		1		1
Exchange | Level 3
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	149	216	183	169
Included in earnings	4	3	17	14
Included in other comprehensive income	1	1	0	3
Purchases	0	1	9	2
Sales	(10)	(15)	(57)	(27)
Transfers in and (out) of Level 3	0	(23)	(8)	22
Ending balance	144	183	144	183
Exchange | Level 3 | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	35	95	59	55
Included in earnings	1	(1)	5	0
Included in other comprehensive income	1	1	0	3
Purchases	0	0	5	1
Sales	(6)	(13)	(30)	(22)
Transfers in and (out) of Level 3	0	(23)	(8)	22
Ending balance	31	59	31	59
Exchange | Level 3 | Trading securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	14	13	15	12
Included in earnings	1	2	1	3
Included in other comprehensive income	0	0	0	0
Purchases	0	0	4	0
Sales	0	0	(5)	0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	15	15	15	15
Exchange | Level 3 | Fixed maturities | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	35	89	59	50
Included in earnings	1	(1)	3	0
Included in other comprehensive income	1	1	1	3
Purchases	0	0	1	1
Sales	(6)	(13)	(20)	(22)
Transfers in and (out) of Level 3	0	(17)	(13)	27
Ending balance	31	59	31	59
Exchange | Level 3 | States & political subdivisions | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance		4		4
Included in earnings		(1)		(1)
Included in other comprehensive income		1		1
Purchases		0		0
Sales		(4)		(4)
Transfers in and (out) of Level 3		0		0
Ending balance		0		0
Exchange | Level 3 | Corporate debt securities | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	26	34	43	12
Included in earnings	0	0	0	0
Included in other comprehensive income	0	0	0	2
Purchases	0	0	1	1
Sales	0	0	(3)	(5)
Transfers in and (out) of Level 3	0	9	(15)	33
Ending balance	26	43	26	43
Exchange | Level 3 | Commercial mortgage-backed securities | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance			0
Included in earnings			0
Included in other comprehensive income			0
Purchases			0
Sales			(1)
Transfers in and (out) of Level 3			1
Ending balance	0		0
Exchange | Level 3 | Collateralized debt obligations | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	9	46	16	29
Included in earnings	1	0	3	1
Included in other comprehensive income	1	0	1	0
Purchases	0	0	0	0
Sales	(6)	(9)	(16)	(13)
Transfers in and (out) of Level 3	0	(21)	1	(1)
Ending balance	5	16	5	16
Exchange | Level 3 | Other debt securities | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance		5		5
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		(5)		(5)
Ending balance		0		0
Exchange | Level 3 | Nonredeemable preferred stock | Available-for-sale securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance		6	0	5
Included in earnings		0	2	0
Included in other comprehensive income		0	(1)	0
Purchases		0	4	0
Sales		0	(10)	0
Transfers in and (out) of Level 3		(6)	5	(5)
Ending balance	0	0	0	0
Exchange | Level 3 | Common stock | Trading securities
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	14	13	15	12
Included in earnings	1	2	1	3
Included in other comprehensive income	0	0	0	0
Purchases	0	0	4	0
Sales	0	0	(5)	0
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	15	15	15	15
Exchange | Level 3 | Real estate | Limited partnerships
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Beginning balance	100	108	109	102
Included in earnings	2	2	11	11
Included in other comprehensive income	0	0	0	0
Purchases	0	1	0	1
Sales	(4)	(2)	(22)	(5)
Transfers in and (out) of Level 3	0	0	0	0
Ending balance	98	109	98	109
Fair value measurements on a recurring basis
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Ending balance	164		164
Fair value measurements on a recurring basis | Indemnity
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Ending balance	20		20
Fair value measurements on a recurring basis | Indemnity | Real estate
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Ending balance	18		18
Fair value measurements on a recurring basis | Exchange
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Ending balance	144		144
Fair value measurements on a recurring basis | Exchange | Real estate
Roll forward of Level 3 consolidated fair value measurements on a recurring basis
Ending balance	$ 98		$ 98