Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Income tax expense	$ 474.8	$ 456.3	$ 1,877.6	$ 1,427.6
Effective tax rate	42.00%	42.00%	44.10%	41.00%
Health Insurance Provider Fee, increase in nondeductible income tax expense	$ 89.3	$ 73.5	$ 316.8	$ 234.5