Fair Value Measurements - Recurring basis (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Level 1 | Fair Value
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	$ 34	$ 39
Level 2 | Fair Value | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative assets		196
Derivative liabilities	7,858	6,251
Level 2 | Fair Value | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	3,017	1,551
Level 3 | Fair Value | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	20	$ 55
Fair value on a recurring basis | Fair Value
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	34
Fair value on a recurring basis | Fair Value | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative liabilities	7,858
Fair value on a recurring basis | Fair Value | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	3,017
Fair value on a recurring basis | Fair Value | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	20
Fair value on a recurring basis | Level 1
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	34
Fair value on a recurring basis | Level 2 | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative liabilities	7,858
Fair value on a recurring basis | Level 2 | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	3,017
Fair value on a recurring basis | Level 3 | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	$ 20