Fair Value Measurements (Details) - Level 2 - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Interest rate derivative financial instruments	$ 18,548	$ 9,501
Total	20,618	10,358
Liabilities:
Interest rate derivative financial instruments	2,279	10,579
Total	2,279	10,579
Investments
Assets:
Investments	2,057	844
Demand obligations
Assets:
Investments	$ 13	$ 13

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

+ References

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Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Fair value of financial and nonfinancial obligations.

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