Long-Term Debt - Net Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Debt Disclosure [Abstract]
Interest expense	$ 10,240	$ 13,044
Interest income	(346)	(444)
Capitalized interest	(4,668)	(1,916)
Net interest expense	$ 5,226	$ 10,684