Non-operating (loss) income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Non-operating (loss) income, net [Abstract]
Unrealized Gain (Loss) on Derivatives	$ (94)	$ 2,708	$ 971	$ (4,311)
Interest Income	1,522	373	2,564	632
Other Nonoperating Income (Expense)	281	120	1,295	1,325
Nonoperating (loss) Income	$ 1,709	$ 3,201	$ 4,830	$ (2,354)