Long-Term Debt - Net Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Debt Disclosure [Abstract]
Interest expense	$ 10,745	$ 10,897	$ 34,224	$ 29,057
Interest income	(833)	(470)	(1,713)	(1,577)
Capitalized interest	(3,069)	(1,714)	(7,504)	(9,462)
Net interest expense	$ 6,843	$ 8,713	$ 25,007	$ 18,018