Fair Value Measurements (Details) - Recurring basis - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets/(Liabilities) at Fair Value
Fair Value Measurements at Reporting Date
Derivative assets	$ 2,152	$ 3,901
Derivative liabilities	(7,432)	(9,712)
Quoted Prices in Active Markets for Identical Assets/(Liabilities) (Level 1)
Fair Value Measurements at Reporting Date
Derivative assets	22	1
Derivative liabilities	(7,432)	(9,712)
Significant Other Observable Inputs (Level 2)
Fair Value Measurements at Reporting Date
Derivative assets	$ 2,130	$ 3,900