Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income tax expense	$ 518.7	$ 474.8	$ 1,795.4	$ 1,877.6
Effective tax rate	45.60%	42.00%	46.10%	44.10%
Health Insurance Provider Fee, increase in nondeductible income tax expense	$ 100.5	$ 89.3	$ 308.8	$ 316.8