Basis of Presentation and Nature of Operations - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) Segment	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)
Accounting Policies [Abstract]
Number of operating segments | Segment	2
Income tax expense from remeasurement of deferred tax assets and liabilities related to Tax Cuts and Jobs Act		$ 64.6
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating income	$ 39.6		$ 34.4
Nonoperating expense	$ 20.9		25.2
Reclassifications due to Adoption | ASU 2017-07 - NPPC
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating income			18.3
Nonoperating expense			$ 18.3