Segment Information - Non-insurance Revenue from Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	$ 320	$ 314
Other revenues	17	53
Non-insurance revenues with customers	341	339
Installment billing fees [Member] | Operating Segments [Member] | Property and Casualty, Commercial Insurance [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	8	9
Installment billing fees [Member] | Operating Segments [Member] | Property and Casualty, Personal Insurance [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	9	9
Insurance servicing fees [Member] | Operating Segments [Member] | Property and Casualty, Personal Insurance [Member]
Segment Reporting Information [Line Items]
Other revenues	19	19
Administrative services fees [Member] | Operating Segments [Member] | Group Insurance Policy [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	43	45
Advisor, distribution and other management fees [Member] | Operating Segments [Member] | Mutual Fund [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	224	217
Other fees [Member] | Operating Segments [Member] | Mutual Fund [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	23	21
Investment management and other fees [Member] | Corporate
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	13	13
Transaction service fees [Member] | Corporate
Segment Reporting Information [Line Items]
Other revenues	$ 2	$ 6