Stock-Based Compensation (Net Tax Windfall) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Balance at December 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accumulated tax windfall in additional contributed capital		$ 52.4
2015 Net Windfall Resulting From Exercises and Conversions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accumulated tax windfall in additional contributed capital	$ 15.5
Balance at December 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accumulated tax windfall in additional contributed capital	$ 67.9