Derivatives (Classification on the Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings from equity method investments \| Interest rate swaps \| Designated as hedge
Derivative financial instruments on consolidated statements of operations
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income	$ 1,157	$ (93)	$ 3,508	$ (15)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Earnings	81	(62)	90	(150)
Earnings from equity method investments \| Interest rate cap \| Designated as hedge
Derivative financial instruments on consolidated statements of operations
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income		(9)		(14)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Earnings		(9)		(14)
Earnings from equity method investments \| Foreign exchange contracts \| Designated as hedge
Derivative financial instruments on consolidated statements of operations
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income		(70)		(369)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Earnings		0		0
Interest Expense \| Interest rate swaps \| Designated as hedge
Derivative financial instruments on consolidated statements of operations
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income	(1,150)	(44)	(1,150)	424
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Earnings	0	384	0	355
Other Expense \| Interest rate cap \| Not designated as hedge
Derivative financial instruments on consolidated statements of operations
Amount of Gain (Loss) Recognized in Income	0	(41)	0	6
Other Expense \| Foreign exchange contracts \| Not designated as hedge
Derivative financial instruments on consolidated statements of operations
Amount of Gain (Loss) Recognized in Income	$ 0	$ (645)	$ 0	$ (769)

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959

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The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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