Long-Term Debt - Interest Expense And Capitalized Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Interest expense	$ 32,617	$ 38,274	$ 45,110
Interest income	(3,237)	(2,590)	(2,086)
Capitalized interest	(15,629)	(16,906)	(11,785)
Net interest expense	$ 13,751	$ 18,778	$ 31,239