Fair Value Measurements - Recurring basis (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair value on a recurring basis | Level 1
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	$ 24
Fair value on a recurring basis | Level 2 | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative liabilities	7,384
Fair value on a recurring basis | Level 2 | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	2,469
Fair value on a recurring basis | Level 3 | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	16
Fair Value | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	2,469	$ 1,551
Fair Value | Level 1
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	24	39
Fair Value | Level 2 | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative assets		196
Derivative liabilities	7,384	6,251
Fair Value | Level 3 | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	16	$ 55
Fair Value | Fair value on a recurring basis
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	24
Fair Value | Fair value on a recurring basis | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative liabilities	7,384
Fair Value | Fair value on a recurring basis | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	2,469
Fair Value | Fair value on a recurring basis | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	$ 16