Investments (Narrative) (Details) $ in Millions	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Gain (Loss) on Investments
Largest single common stock holding	$ 414
Largest equity holdings to total equity portfolio	5.50%
Largest equity holdings to total portfolio	2.10%
Assets Held by Insurance Regulators	$ 117	$ 112
Collateral at fair value	$ 95	$ 75
Impaired securities	3	1	6
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss	$ 3	$ 58	$ 18
Fixed Maturities
Gain (Loss) on Investments
Number of securities total unrealized loss in an unrealized loss position for 12 months or more	38	400	249
Number of securities below 70 percent of amortized cost	0	0	0
Equity Securities
Gain (Loss) on Investments
Number of securities total unrealized loss in an unrealized loss position for 12 months or more			0