Goodwill and Intangible Assets, net - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) acquisition	Mar. 31, 2017 USD ($)
Goodwill [Line Items]
Number of acquisitions | acquisition	1
Goodwill	$ 669.0
Amortization expense	15.4	$ 8.5
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2018	56.7
2019	77.8
2020	76.2
2021	74.5
2022	66.1
2023	59.5
Aclara
Goodwill [Line Items]
Goodwill	$ 669.0