Segment Information - Non-insurance Revenue from Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	$ 314	$ 323
Other revenues	53	20
Non-insurance revenues with customers	339	342
Installment billing fees [Member] | Operating Segments [Member] | Property and Casualty, Commercial Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	9	9
Installment billing fees [Member] | Operating Segments [Member] | Property and Casualty, Personal Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	9	10
Insurance servicing fees [Member] | Operating Segments [Member] | Property and Casualty, Personal Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Other revenues	19	19
Administrative services fees [Member] | Operating Segments [Member] | Group Insurance Policies [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	45	44
Advisor, distribution and other management fees [Member] | Operating Segments [Member] | Mutual Fund [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	217	238
Other fees [Member] | Operating Segments [Member] | Mutual Fund [Member]
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	21	20
Investment management and other fees [Member] | Corporate
Segment Reporting Information [Line Items]
Insurance Commissions and Fees	13	2
Transaction service fees [Member] | Corporate
Segment Reporting Information [Line Items]
Other revenues	$ 6	$ 0