Derivative Financial Instruments - Cash Receipts on Derivative Settlements, Net Included within Net Cash Provided by Operating Activities (Details) $ in Thousands  | 
3 Months Ended | 
|---|---|
| 
 Mar. 31, 2019  
USD ($) 
 | |
| Derivative Instruments And Hedging Activities Disclosure [Abstract] | |
| Cash receipts on derivative settlements, net | $ 11,948 | 
| X | ||||||||||
- References No definition available. 
  | 
| X | ||||||||||
- Definition Cash proceeds payments on derivative settlements net operating activities. No definition available. 
  |