Stock-Based Compensation (Fair Value and Tax Deductions of Restricted Stock Units Vested) (Details) - Restricted Stock Units [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares or units distributed	$ 19.7	$ 19.5	$ 11.1
Realized tax benefits from tax deductions	$ 7.5	$ 7.4	$ 4.3