Income Taxes (Differences Between The 35 Percent Statutory Income Tax Rate And Effective Income Tax Rate) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at statutory rate:	$ 256	$ 284	$ 308
Tax at statutory rate (percentage):	35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Tax-exempt income from municipal bonds	$ (36)	$ (34)	$ (33)
Dividend received exclusion	(34)	(33)	(32)
Deferred tax benefit due to tax rate change	(495)	0	0
Other	(6)	4	4
Total provision (benefit) for income taxes	$ (315)	$ 221	$ 247
Tax at statutory rate:
Tax-exempt income from municipal bonds (percentage)	(4.90%)	(4.20%)	(3.70%)
Dividend received exclusion (percentage)	(4.70%)	(4.10%)	(3.60%)
Deferred tax benefit due to tax rate change	(67.80%)	0.00%	0.00%
Other (percentage)	(0.80%)	0.50%	0.30%
Effective tax, percentage	(43.20%)	27.20%	28.00%