Revenue Revenue (Details) |
9 Months Ended | 12 Months Ended |
---|---|---|
Sep. 30, 2018
USD ($)
|
Dec. 31, 2018
USD ($)
|
|
Disaggregation of Revenue [Line Items] | ||
Number of Types of Performance Obligations | 2 | |
Contract with Customer, Liability, Revenue Recognized | $ 20,200,000 | |
Contract with Customer, Refund Liability | $ 0 | |
Stand Ready Performance Obligations [Member] | ||
Disaggregation of Revenue [Line Items] | ||
Revenue, Performance Obligation, Description of Good or Service | those that require us to stand ready to provide goods and services to a customer to use as and when requested (“Stand Ready Performance Obligations”) | |
Other Performance Obligations [Member] | ||
Disaggregation of Revenue [Line Items] | ||
Revenue, Performance Obligation, Description of Good or Service | those that do not require us to stand ready (“Other Performance Obligations”) |