Fair Value of Financial Instruments - Assets and Liabilities at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Derivative financial instruments, asset	$ 1,999	$ 1,529
Liabilities:
Derivative financial instrument, liability	548	1,089
Fair Value, Measurements, Recurring
Assets:
Derivative financial instruments, asset	1,999	1,529
Liabilities:
Derivative financial instrument, liability	548	1,089
Fair Value, Measurements, Recurring \| Level 1
Assets:
Derivative financial instruments, asset	0	0
Liabilities:
Derivative financial instrument, liability	0	0
Fair Value, Measurements, Recurring \| Level 2
Assets:
Derivative financial instruments, asset	1,999	1,529
Liabilities:
Derivative financial instrument, liability	548	1,089
Fair Value, Measurements, Recurring \| Level 3
Assets:
Derivative financial instruments, asset	0	0
Liabilities:
Derivative financial instrument, liability	$ 0	$ 0

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=SL51823488-111719

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant