Derivative Instruments - Gain (Loss) On Derivative Instruments (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]      
Net gain (loss) on derivative instruments $ (1,561) $ 15,336 $ 5,138