Financial Derivatives (Futures) (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Derivative [Line Items]
Fair Value	$ (11,548)
Short \| U.S. Treasury futures
Derivative [Line Items]
Notional Amount	(151,600)
Fair Value	$ (2,380)
Remaining Years to Maturity	2 months 24 days
Short \| Eurodollar futures
Derivative [Line Items]
Notional Amount	$ (63,000)
Fair Value	$ (74)
Remaining Years to Maturity	5 months 29 days
Short \| Currency futures
Derivative [Line Items]
Notional Amount	$ (15,840)
Fair Value	$ 138
Remaining Years to Maturity	2 months 19 days
Short \| Futures
Derivative [Line Items]
Notional Amount	$ (230,440)
Fair Value	$ (2,316)
Remaining Years to Maturity	3 months 20 days

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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Namespace Prefix:	invest_
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Balance Type:	na
Period Type:	instant

- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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