Derivatives (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Location and amount of gains (losses) on derivative instruments and related hedged items
Total	$ 0	$ 0	$ 0
Interest expense [Member] \| Interest rate swap [Member]
Location and amount of gains (losses) on derivative instruments and related hedged items
Derivative: Interest rate swap	(3,341)	(8,554)	(5,118)
Interest expense [Member] \| Fixed-rate debt [Member]
Location and amount of gains (losses) on derivative instruments and related hedged items
Hedged item: Fixed-rate debt	$ 3,341	$ 8,554	$ 5,118

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The net gain (loss) recognized in earnings during the period due to the ineffectiveness on interest rate fair value hedges.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

+ Details

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- Definition

Amount of unrealized gain (loss) included in earnings related to the fair value of the hedged item in an interest rate fair value hedge, offset by the gain (loss) on the hedging instrument to the extent that the fair value hedge is determined to be effective.

+ References

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=35706170&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)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

+ Details

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- Definition

Amount of unrealized gain (loss) related to the fair value of interest rate derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

+ Details

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