Investments (Investment Income Realized Investment Gains And Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investment income:
Interest	$ 445	$ 440	$ 428
Dividends	170	161	150
Other	4	3	3
Total	619	604	581
Less investment expenses	10	9	9
Total	609	595	572
Realized investment gains and losses:
Other	9	2	1
Total	148	124	70
Fixed Maturities
Realized investment gains and losses:
Gross realized gains	25	26	18
Gross realized losses	0	(1)	0
Other-than-temporary impairments	(6)	(2)	(18)
Equity Securities
Realized investment gains and losses:
Gross realized gains	195	152	129
Gross realized losses	(72)	(53)	(26)
Other-than-temporary impairments	$ (3)	$ 0	$ (34)