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, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax at statutory rate:	$ 308	$ 252	$ 250
Tax at statutory rate (percentage):	35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Tax-exempt income from municipal bonds	$ (33)	$ (33)	$ (32)
Dividend received exclusion	(32)	(29)	(26)
Other	4	6	5
Total provision for income taxes	$ 247	$ 196	$ 197
Tax at statutory rate:
Tax-exempt income from municipal bonds (percentage)	(3.70%)	(4.60%)	(4.50%)
Dividend received exclusion (percentage)	(3.60%)	(4.00%)	(3.60%)
Other (percentage)	0.30%	0.80%	0.70%
Effective tax, percentage	28.00%	27.20%	27.60%