Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Expense
Interest expense before capitalized interest	$ 70,561	$ 78,313	$ 90,729
Amortization of deferred financing costs	3,315	3,217	4,661
Interest expense related to finance lease right-of-use assets	1,450	921	922
Net unrealized	184	50	(926)
Net realized			(135)
Capitalized interest	(13,189)	(29,806)	(20,804)
Interest expense	$ 62,321	$ 52,695	$ 74,447