Goodwill and Other Intangible Assets Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill acquired	$ 88.5	$ 70.0
Year to date amortization expense	34.9	$ 32.3	$ 28.2
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Amortization expense, 2018	35.7
Amortization expense, 2019	33.2
Amortization expense, 2020	33.8
Amortization expense, 2021	33.2
Amortization expense, 2022	$ 31.7