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, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Tax at statutory rate:	$ 284	$ 308	$ 252
Tax at statutory rate (percentage):	35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Tax-exempt income from municipal bonds	$ (34)	$ (33)	$ (33)
Dividend received exclusion	(33)	(32)	(29)
Other	4	4	6
Total provision for income taxes	$ 221	$ 247	$ 196
Tax at statutory rate:
Tax-exempt income from municipal bonds (percentage)	(4.20%)	(3.70%)	(4.60%)
Dividend received exclusion (percentage)	(4.10%)	(3.60%)	(4.00%)
Other (percentage)	0.50%	0.30%	0.80%
Effective tax, percentage	27.20%	28.00%	27.20%