Segment Information - Non-insurance Revenue from Customers (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	$ 330	$ 344	$ 970	$ 994
Other revenues	44	29	129	73
Non-insurance revenues with customers	359	373	1,052	1,067
Installment billing fees [Member] | Operating Segments [Member] | Property and Casualty, Commercial Insurance [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	8	9	26	26
Installment billing fees [Member] | Operating Segments [Member] | Property and Casualty, Personal Insurance [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	9	10	28	30
Insurance servicing fees [Member] | Operating Segments [Member] | Property and Casualty, Personal Insurance [Member]
Segment Reporting Information [Line Items]
Other revenues	23	24	65	66
Administrative services fees [Member] | Operating Segments [Member] | Group Insurance Policy [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	45	43	135	131
Advisor, distribution and other management fees [Member] | Operating Segments [Member] | Mutual Fund [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	232	245	677	722
Other fees [Member] | Operating Segments [Member] | Mutual Fund [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	22	21	65	63
Investment management and other fees [Member] | Corporate
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	14	15	38	21
Transaction service fees [Member] | Corporate
Segment Reporting Information [Line Items]
Other revenues	$ 6	$ 6	$ 18	$ 8