Revenues (Narrative - Performance Obligations) (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01 |
3 Months Ended |
|---|---|
|
Jun. 30, 2018
USD ($)
| |
| Revenue from Contract with Customer [Abstract] | |
| Revenue, remaining performance obligation, amount | $ 302,397,000 |
| Revenue, remaining performance obligation, amount next six months | $ 157,438,000 |
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] | |
| Revenue, remaining performance obligation, period | 9 months |