Quarterly report pursuant to Section 13 or 15(d)

Accounts Receivable and Revenues from Contracts with Customers - Additional Information (Details)

v3.19.1
Accounts Receivable and Revenues from Contracts with Customers - Additional Information (Details)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2019
USD ($)
Customer
Mar. 31, 2018
USD ($)
Customer
Dec. 31, 2018
USD ($)
Sales Revenue | Customer Concentration Risk [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Number of major customers | Customer 3 3  
Revenues, major customers $ 69.0 $ (70.6)  
Concentration risk, percentage 66.00% 91.00%  
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 1      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Revenues, major customers $ (39.9)    
Concentration risk, percentage 38.00%    
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 2      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Revenues, major customers $ (14.5)    
Concentration risk, percentage 14.00%    
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 3      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Revenues, major customers $ (14.6)    
Concentration risk, percentage 14.00%    
Accounts Receivable | Credit Concentration Risk      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Concentration risk, percentage 70.00%   59.00%
Accounts receivable, major customers $ 42.9   $ 34.8