Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating revenues
Net earned premiums	$ 1,962	$ 1,869
Net investment income	504	329
Non-insurance warranty revenue	338	301
Other revenues	5	8
Total operating revenues	2,809	2,507
Claims, Benefits and Expenses
Net incurred claims and benefits	1,500	1,419
Policyholders’ dividends	6	6
Amortization of deferred acquisition costs	359	344
Non-insurance warranty expense	311	281
Other insurance related expenses	255	258
Other expenses	57	72
Total claims, benefits and expenses	2,488	2,380
Core income (loss) before income tax	321	127
Income tax (expense) benefit on core income (loss)	(58)	(19)
Core income (loss)	263	108
Net investment gains (losses)	57	(216)
Income tax (expense) benefit on net investment gains (losses)	(8)	47
Net investment gains (losses), after tax	49	(169)
Net income (loss)	312	(61)
Operating Segments | Specialty
Operating revenues
Net earned premiums	735	685
Net investment income	117	56
Non-insurance warranty revenue	338	301
Other revenues	0	1
Total operating revenues	1,190	1,043
Claims, Benefits and Expenses
Net incurred claims and benefits	427	405
Policyholders’ dividends	1	1
Amortization of deferred acquisition costs	154	151
Non-insurance warranty expense	311	281
Other insurance related expenses	70	69
Other expenses	11	13
Total claims, benefits and expenses	974	920
Core income (loss) before income tax	216	123
Income tax (expense) benefit on core income (loss)	(46)	(27)
Core income (loss)	170	96
Operating Segments | Commercial
Operating revenues
Net earned premiums	855	818
Net investment income	148	42
Non-insurance warranty revenue	0	0
Other revenues	5	8
Total operating revenues	1,008	868
Claims, Benefits and Expenses
Net incurred claims and benefits	639	555
Policyholders’ dividends	5	5
Amortization of deferred acquisition costs	153	144
Non-insurance warranty expense	0	0
Other insurance related expenses	115	127
Other expenses	9	6
Total claims, benefits and expenses	921	837
Core income (loss) before income tax	87	31
Income tax (expense) benefit on core income (loss)	(18)	(8)
Core income (loss)	69	23
Operating Segments | International
Operating revenues
Net earned premiums	252	239
Net investment income	14	15
Non-insurance warranty revenue	0	0
Other revenues	0	0
Total operating revenues	266	254
Claims, Benefits and Expenses
Net incurred claims and benefits	155	154
Policyholders’ dividends	0	0
Amortization of deferred acquisition costs	52	49
Non-insurance warranty expense	0	0
Other insurance related expenses	35	36
Other expenses	(5)	13
Total claims, benefits and expenses	237	252
Core income (loss) before income tax	29	2
Income tax (expense) benefit on core income (loss)	(5)	0
Core income (loss)	24	2
Operating Segments | Life & Group
Operating revenues
Net earned premiums	120	127
Net investment income	219	208
Non-insurance warranty revenue	0	0
Other revenues	1	0
Total operating revenues	340	335
Claims, Benefits and Expenses
Net incurred claims and benefits	281	316
Policyholders’ dividends	0	0
Amortization of deferred acquisition costs	0	0
Non-insurance warranty expense	0	0
Other insurance related expenses	25	26
Other expenses	2	3
Total claims, benefits and expenses	308	345
Core income (loss) before income tax	32	(10)
Income tax (expense) benefit on core income (loss)	4	14
Core income (loss)	36	4
Operating Segments | Corporate & Other
Operating revenues
Net earned premiums	0	0
Net investment income	6	8
Non-insurance warranty revenue	0	0
Other revenues	1	1
Total operating revenues	7	9
Claims, Benefits and Expenses
Net incurred claims and benefits	(2)	(11)
Policyholders’ dividends	0	0
Amortization of deferred acquisition costs	0	0
Non-insurance warranty expense	0	0
Other insurance related expenses	10	0
Other expenses	42	39
Total claims, benefits and expenses	50	28
Core income (loss) before income tax	(43)	(19)
Income tax (expense) benefit on core income (loss)	7	2
Core income (loss)	(36)	(17)
Eliminations
Operating revenues
Net earned premiums	0	0
Net investment income	0	0
Non-insurance warranty revenue	0	0
Other revenues	(2)	(2)
Total operating revenues	(2)	(2)
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	0
Other expenses	(2)	(2)
Total claims, benefits and expenses	(2)	(2)
Core income (loss) before income tax	0	0
Income tax (expense) benefit on core income (loss)	0	0
Core income (loss)	$ 0	$ 0