Income Taxes (Reconciliation Of Income Tax Expense Computed At The Statutory Federal Income Tax Rate) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Amount at statutory rate, amount	$ 1,594.4	$ 1,620.9	$ 1,528.8
Amount at statutory rate, percent	35.00%	35.00%	35.00%
State and local income taxes net of federal tax benefit, amount	$ 61.5	$ 75.3	$ 49.0
State and local income taxes net of federal tax benefit, percent	1.40%	1.60%	1.10%
Tax exempt interest and dividends received deduction, amount	$ (61.7)	$ (63.2)	$ (65.9)
Tax exempt interest and dividends received deduction, percent	(1.40%)	(1.30%)	(1.50%)
Health Insurance Provider fee, amount	$ 411.7	$ 422.6	$ 312.6
Health Insurance Provider fee, percent	9.00%	9.10%	7.20%
Other, net amount	$ 79.7	$ 15.4	$ (16.5)
Other, net percent	1.80%	0.30%	(0.40%)
Total income tax expense	$ 2,085.6	$ 2,071.0	$ 1,808.0
Total income tax expense, percent	45.80%	44.70%	41.40%