Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating revenues
Net earned premiums	$ 1,869	$ 1,803
Net investment income	329	571
Non-insurance warranty revenue	301	281
Other revenues	8	9
Total operating revenues	2,507	2,664
Claims, Benefits and Expenses
Net incurred claims and benefits	1,419	1,351
Policyholders’ dividends	6	6
Amortization of deferred acquisition costs	344	342
Non-insurance warranty expense	281	260
Other insurance related expenses	258	251
Other expenses	72	66
Total claims, benefits and expenses	2,380	2,276
Core income (loss) before income tax	127	388
Income tax (expense) benefit on core income (loss)	(19)	(70)
Core income (loss)	108	318
Net investment gains (losses)	(216)	31
Income tax (expense) benefit on net investment gains (losses)	47	(7)
Net investment gains (losses), after tax	(169)	24
Net income (loss)	(61)	342
Operating Segments | Specialty
Operating revenues
Net earned premiums	685	661
Net investment income	56	155
Non-insurance warranty revenue	301	281
Other revenues	1	1
Total operating revenues	1,043	1,098
Claims, Benefits and Expenses
Net incurred claims and benefits	405	392
Policyholders’ dividends	1	1
Amortization of deferred acquisition costs	151	147
Non-insurance warranty expense	281	260
Other insurance related expenses	69	70
Other expenses	13	12
Total claims, benefits and expenses	920	882
Core income (loss) before income tax	123	216
Income tax (expense) benefit on core income (loss)	(27)	(47)
Core income (loss)	96	169
Operating Segments | Commercial
Operating revenues
Net earned premiums	818	763
Net investment income	47	190
Non-insurance warranty revenue	0	0
Other revenues	7	7
Total operating revenues	872	960
Claims, Benefits and Expenses
Net incurred claims and benefits	558	510
Policyholders’ dividends	5	5
Amortization of deferred acquisition costs	144	127
Non-insurance warranty expense	0	0
Other insurance related expenses	127	130
Other expenses	6	11
Total claims, benefits and expenses	840	783
Core income (loss) before income tax	32	177
Income tax (expense) benefit on core income (loss)	(8)	(38)
Core income (loss)	24	139
Operating Segments | International
Operating revenues
Net earned premiums	239	250
Net investment income	15	15
Non-insurance warranty revenue	0	0
Other revenues	0	0
Total operating revenues	254	265
Claims, Benefits and Expenses
Net incurred claims and benefits	154	162
Policyholders’ dividends	0	0
Amortization of deferred acquisition costs	49	68
Non-insurance warranty expense	0	0
Other insurance related expenses	36	25
Other expenses	13	4
Total claims, benefits and expenses	252	259
Core income (loss) before income tax	2	6
Income tax (expense) benefit on core income (loss)	0	0
Core income (loss)	2	6
Operating Segments | Life & Group
Operating revenues
Net earned premiums	127	130
Net investment income	208	204
Non-insurance warranty revenue	0	0
Other revenues	0	1
Total operating revenues	335	335
Claims, Benefits and Expenses
Net incurred claims and benefits	316	308
Policyholders’ dividends	0	0
Amortization of deferred acquisition costs	0	0
Non-insurance warranty expense	0	0
Other insurance related expenses	26	28
Other expenses	3	2
Total claims, benefits and expenses	345	338
Core income (loss) before income tax	(10)	(3)
Income tax (expense) benefit on core income (loss)	14	13
Core income (loss)	4	10
Operating Segments | Corporate & Other
Operating revenues
Net earned premiums	0	0
Net investment income	3	7
Non-insurance warranty revenue	0	0
Other revenues	2	2
Total operating revenues	5	9
Claims, Benefits and Expenses
Net incurred claims and benefits	(14)	(21)
Policyholders’ dividends	0	0
Amortization of deferred acquisition costs	0	0
Non-insurance warranty expense	0	0
Other insurance related expenses	0	(1)
Other expenses	39	39
Total claims, benefits and expenses	25	17
Core income (loss) before income tax	(20)	(8)
Income tax (expense) benefit on core income (loss)	2	2
Core income (loss)	(18)	(6)
Eliminations
Operating revenues
Net earned premiums	0	(1)
Net investment income	0	0
Non-insurance warranty revenue	0	0
Other revenues	(2)	(2)
Total operating revenues	(2)	(3)
Claims, Benefits and Expenses
Net incurred claims and benefits	0	0
Policyholders’ dividends	0	0
Amortization of deferred acquisition costs	0	0
Non-insurance warranty expense	0	0
Other insurance related expenses	0	(1)
Other expenses	(2)	(2)
Total claims, benefits and expenses	(2)	(3)
Core income (loss) before income tax	0	0
Income tax (expense) benefit on core income (loss)	0	0
Core income (loss)	$ 0	$ 0