Long-Term Debt - Components Of Net Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt Disclosure [Abstract]
Interest expense	$ 8,045	$ 8,041	$ 15,941	$ 16,340
Interest income	(675)	(679)	(1,433)	(1,269)
Capitalized interest	(5,165)	(3,763)	(10,205)	(7,576)
Net interest expense	$ 2,205	$ 3,599	$ 4,303	$ 7,495