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Derivative Instruments - Cash flow hedges (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Effects of derivative instruments |  |  |
Amount of Gain Recognized in OCI on Derivatives (Effective Portion) | $ 1,957,000 | $ (799,000) | $ (796,000)
Cash Flow Hedging |  |  |
Effects of derivative instruments |  |  |
Amount of Gain Recognized in OCI on Derivatives (Effective Portion) | 896,000 | 69,000 |
Amount of Loss (Gain) Reclassified from Accumulated OCI into Income (Effective Portion) | 621,000 | 25,000 |
Significant ineffectiveness on held hedges | 0 |  |
Cash Flow Hedging | Interest rate contracts | Interest expense Member |  |  |
Effects of derivative instruments |  |  |
Amount of Gain Recognized in OCI on Derivatives (Effective Portion) | 896,000 | 69,000 |
Amount of Loss (Gain) Reclassified from Accumulated OCI into Income (Effective Portion) | $ 621,000 | $ 25,000 |

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- Definition 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. + 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 (b) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 + Details
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- Definition Represents the portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing the amount of significant hedge ineffectiveness. + References No definition available. + Details
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