Changes in Shareholders' Equity Changes in Shareholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity Attributable to Parent	$ 2,033.4		$ 2,033.4
Net Income			36.3
Other Comprehensive Income	22.5	$ 70.4	39.6	$ 136.8
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 59.1	$ 74.4	75.9	$ 138.7
Cash Dividends and Dividend Equivalents to Shareholders ($0.48 per share)			24.7
Equity-based Compensation Cost			5.7
Equity-based Awards, Net of Shares Exchanged			0.8
Stockholders' Equity Attributable to Parent			$ 1,975.2
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					$ 0.5