Investments (Narrative) (Details) $ in Millions	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Gain (Loss) on Investments
Largest single common stock holding	$ 255
Largest equity holdings to total equity portfolio	4.40%
Largest equity holdings to total portfolio	1.50%
Investments in fair value, deposit with various states	$ 17,434	$ 17,774
Collateral at fair value	$ 75	$ 57
Impaired securities	1	6	4
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss	$ 58	$ 18	$ 11
Fixed Maturities
Gain (Loss) on Investments
Number of securities total unrealized loss in an unrealized loss position for 12 months or more	400	249	32
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	0
On Deposit With Various States
Gain (Loss) on Investments
Investments in fair value, deposit with various states	$ 112	$ 101