Accounts Receivable and Revenues from Contracts with Customers - Additional Information (Details) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) Customer	Sep. 30, 2017 USD ($) Customer	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 2.7
Sales Revenue | Customer Concentration Risk [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of major customers | Customer	3	2
Revenues, major customers	$ 254.5	$ 85.9
Concentration risk, percentage	81.00%	82.00%
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 126.6
Concentration risk, percentage	40.00%
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 65.9
Concentration risk, percentage	21.00%
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 62.0
Concentration risk, percentage	20.00%
Accounts Receivable | Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage	51.00%		82.00%
Accounts receivable, major customers	$ 32.9		$ 32.1