Fair Value Measurements - Recurring basis (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Fair value assets and liabilities measured on recurring basis:
Financial assets or liabilities	$ 0
Level 1 | Fair Value
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	37	$ 39
Level 2 | Fair Value | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative assets		196
Derivative liabilities	6,558	6,251
Level 2 | Fair Value | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	2,901	1,551
Level 3 | Fair Value | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	18	$ 55
Fair value on a recurring basis | Fair Value
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	37
Fair value on a recurring basis | Fair Value | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative liabilities	6,558
Fair value on a recurring basis | Fair Value | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	2,901
Fair value on a recurring basis | Fair Value | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	18
Fair value on a recurring basis | Level 1
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	37
Fair value on a recurring basis | Level 2 | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative liabilities	6,558
Fair value on a recurring basis | Level 2 | Currency Swap
Fair value assets and liabilities measured on recurring basis:
Derivative assets	2,901
Fair value on a recurring basis | Level 3 | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	$ 18