Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating Revenues
Net earned premiums	$ 1,730	$ 1,735	$ 3,429	$ 3,422
Net investment income	502	500	937	1,058
Other revenues	100	92	197	189
Total operating revenues	2,332	2,327	4,563	4,669
Claims, Benefits and Expenses
Net incurred claims and benefits	1,335	1,466	2,739	2,801
Policyholders' dividends	4	3	8	7
Amortization of deferred acquisition costs	305	314	612	617
Other insurance related expenses	270	259	547	527
Other expenses	146	121	292	250
Total claims, benefits and expenses	2,060	2,163	4,198	4,202
Operating income (loss) before income tax	272	164	365	467
Income tax (expense) benefit on operating income (loss)	(71)	(32)	(73)	(110)
Net operating income (loss)	201	132	292	357
Net realized investment gains (losses), pre-tax	16	0	(20)	10
Income tax (expense) benefit on net realized investment gains (losses)	(8)	6	3	4
Net realized investment gains (losses), after tax	8	6	(17)	14
Net Income (Loss)	209	138	275	371
Specialty [Member]
Operating Revenues
Net earned premiums	702	689	1,384	1,369
Net investment income	133	134	240	289
Other revenues	89	81	176	159
Total operating revenues	924	904	1,800	1,817
Claims, Benefits and Expenses
Net incurred claims and benefits	377	416	767	845
Policyholders' dividends	1	1	2	2
Amortization of deferred acquisition costs	148	146	292	290
Other insurance related expenses	73	66	148	135
Other expenses	79	69	154	136
Total claims, benefits and expenses	678	698	1,363	1,408
Operating income (loss) before income tax	246	206	437	409
Income tax (expense) benefit on operating income (loss)	(82)	(69)	(146)	(137)
Net operating income (loss)	164	137	291	272
Net realized investment gains (losses), pre-tax	4	0	(7)	4
Income tax (expense) benefit on net realized investment gains (losses)	(2)	0	2	(1)
Net realized investment gains (losses), after tax	2	0	(5)	3
Net Income (Loss)	166	137	286	275
Commercial [Member]
Operating Revenues
Net earned premiums	696	703	1,384	1,381
Net investment income	164	169	290	373
Other revenues	8	9	14	18
Total operating revenues	868	881	1,688	1,772
Claims, Benefits and Expenses
Net incurred claims and benefits	469	507	911	961
Policyholders' dividends	3	2	6	5
Amortization of deferred acquisition costs	117	117	233	234
Other insurance related expenses	130	130	271	257
Other expenses	11	5	16	13
Total claims, benefits and expenses	730	761	1,437	1,470
Operating income (loss) before income tax	138	120	251	302
Income tax (expense) benefit on operating income (loss)	(46)	(42)	(85)	(104)
Net operating income (loss)	92	78	166	198
Net realized investment gains (losses), pre-tax	8	2	(10)	6
Income tax (expense) benefit on net realized investment gains (losses)	(3)	2	3	(1)
Net realized investment gains (losses), after tax	5	4	(7)	5
Net Income (Loss)	97	82	159	203
International [Member]
Operating Revenues
Net earned premiums	197	207	395	398
Net investment income	13	13	25	27
Other revenues	0	(1)	1	(1)
Total operating revenues	210	219	421	424
Claims, Benefits and Expenses
Net incurred claims and benefits	157	114	278	230
Policyholders' dividends	0	0	0	0
Amortization of deferred acquisition costs	40	45	87	80
Other insurance related expenses	37	31	65	68
Other expenses	7	(5)	16	0
Total claims, benefits and expenses	241	185	446	378
Operating income (loss) before income tax	(31)	34	(25)	46
Income tax (expense) benefit on operating income (loss)	4	(12)	4	(15)
Net operating income (loss)	(27)	22	(21)	31
Net realized investment gains (losses), pre-tax	4	1	8	2
Income tax (expense) benefit on net realized investment gains (losses)	(1)	(1)	(2)	(1)
Net realized investment gains (losses), after tax	3	0	6	1
Net Income (Loss)	(24)	22	(15)	32
Life and Group Non-Core [Member]
Operating Revenues
Net earned premiums	136	137	267	275
Net investment income	188	179	375	358
Other revenues	3	0	3	9
Total operating revenues	327	316	645	642
Claims, Benefits and Expenses
Net incurred claims and benefits	340	344	663	684
Policyholders' dividends	0	0	0	0
Amortization of deferred acquisition costs	0	6	0	13
Other insurance related expenses	31	34	64	69
Other expenses	2	5	5	9
Total claims, benefits and expenses	373	389	732	775
Operating income (loss) before income tax	(46)	(73)	(87)	(133)
Income tax (expense) benefit on operating income (loss)	42	49	81	92
Net operating income (loss)	(4)	(24)	(6)	(41)
Net realized investment gains (losses), pre-tax	(2)	(5)	(5)	(4)
Income tax (expense) benefit on net realized investment gains (losses)	(3)	6	(3)	8
Net realized investment gains (losses), after tax	(5)	1	(8)	4
Net Income (Loss)	(9)	(23)	(14)	(37)
Corporate and Other Non-Core [Member]
Operating Revenues
Net earned premiums	0	0	0	0
Net investment income	4	5	7	11
Other revenues	0	3	3	5
Total operating revenues	4	8	10	16
Claims, Benefits and Expenses
Net incurred claims and benefits	(8)	85	120	81
Policyholders' dividends	0	0	0	0
Amortization of deferred acquisition costs	0	0	0	0
Other insurance related expenses	0	(1)	0	(1)
Other expenses	47	47	101	93
Total claims, benefits and expenses	39	131	221	173
Operating income (loss) before income tax	(35)	(123)	(211)	(157)
Income tax (expense) benefit on operating income (loss)	11	42	73	54
Net operating income (loss)	(24)	(81)	(138)	(103)
Net realized investment gains (losses), pre-tax	2	2	(6)	2
Income tax (expense) benefit on net realized investment gains (losses)	1	(1)	3	(1)
Net realized investment gains (losses), after tax	3	1	(3)	1
Net Income (Loss)	(21)	(80)	(141)	(102)
Eliminations [Member]
Operating Revenues
Net earned premiums	(1)	(1)	(1)	(1)
Net investment income	0	0	0	0
Other revenues	0	0	0	(1)
Total operating revenues	(1)	(1)	(1)	(2)
Claims, Benefits and Expenses
Net incurred claims and benefits	0	0	0	0
Policyholders' dividends	0	0	0	0
Amortization of deferred acquisition costs	0	0	0	0
Other insurance related expenses	(1)	(1)	(1)	(1)
Other expenses	0	0	0	(1)
Total claims, benefits and expenses	(1)	(1)	(1)	(2)
Operating income (loss) before income tax	0	0	0	0
Income tax (expense) benefit on operating income (loss)	0	0	0	0
Net operating income (loss)	0	0	0	0
Net realized investment gains (losses), pre-tax	0	0	0	0
Income tax (expense) benefit on net realized investment gains (losses)	0	0	0	0
Net realized investment gains (losses), after tax	0	0	0	0
Net Income (Loss)	$ 0	$ 0	$ 0	$ 0