Accounts Receivable Securitization (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) entity	Dec. 31, 2016 USD ($)	Mar. 03, 2016 USD ($)
Accounts Receivable Securitization
Number of funding entities | entity	2
Capacity of securitization program			$ 110.0
Average collection cycle for accounts receivable (in days)	60 days
Fair value of deferred purchase price notes	$ 62.9	$ 60.0
Trade accounts receivable balance sold	$ 99.5	$ 96.7
LIBOR
Accounts Receivable Securitization
Fixed spread (as a percent)	1.25%