Investments - Unrealized Capital Losses 1 (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) securities	Dec. 31, 2018 USD ($) securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Available For Sale Securities Change in Loss Position	$ 497
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	$ 46	$ 201
More than twelve months below amortized cost, Number of Securities | securities	278,000,000	550
Total Unrealized Capital Losses	$ 63	$ 560
Number of Securities | securities	567,000,000	2,444
Fair value decline below amortized cost greater than 20%
Available-for-sale Securities Including Securities Pledged [Line Items]
More than twelve months below amortized cost, Number of Securities | securities	5
Total Unrealized Capital Losses	$ 7
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	0	$ 0
Total Unrealized Capital Losses	3	0
State, municipalities and political subdivisions
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	0	5
Total Unrealized Capital Losses	0	8
U.S. corporate public securities
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	10	50
Total Unrealized Capital Losses	13	181
U.S. corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	16	66
Total Unrealized Capital Losses	16	106
Foreign corporate public securities and foreign governments
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	3	26
Total Unrealized Capital Losses	3	80
Foreign corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	1	20
Total Unrealized Capital Losses	1	97
Residential mortgage-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	5	21
Total Unrealized Capital Losses	11	32
Commercial mortgage-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	0	12
Total Unrealized Capital Losses	3	28
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Loss	11	1
Total Unrealized Capital Losses	$ 13	$ 28