Commitments and Contingencies - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Customer	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 USD ($)
Commitments And Contingencies Disclosure [Line Items]
Lease expense	$ 5.5	$ 4.2	$ 4.5
Purchase commitments	86.4
Purchase commitments, 2018	78.7
Purchase commitments, 2019	5.6
Purchase commitments, 2020	$ 2.1
Number of customer accounted on accounts receivable balance | Customer	1
Number of customers accounted for 10% or more of accounts receivable | Customer	0	0
Minimum
Commitments And Contingencies Disclosure [Line Items]
Lease agreement expiration year	2018
Maximum
Commitments And Contingencies Disclosure [Line Items]
Lease agreement expiration year	2022
Land | Maximum
Commitments And Contingencies Disclosure [Line Items]
Lease agreement expiration year	2078