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

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

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- Definition

Fixed interest rate related to the interest rate derivative.

+ References

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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.

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- Definition

Date the derivative contract matures, in CCYY-MM-DD format.

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- Definition

Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e689-108580

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-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e637-108580

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Derivative Instruments - Interest rate derivatives and their fair values (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 20, 2018	Apr. 05, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Reclassification of other comprehensive income to interest expense (income)	$ (471)	$ 91		$ (965)	$ 493
Forecast
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Reclassification of other comprehensive income to interest expense (income)			$ 1,600
Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative							$ 400,000	$ 400,000
Interest Rate Swap \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	1,000,000			1,000,000		$ 1,000,000
Fair value	(19,176)			(19,176)		2,343
Swap instrument one matures on December 17, 2021 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 25,000			$ 25,000		25,000
Fixed Rate Per annum	1.989%			1.989%
Expiration Date				Dec. 17, 2021
Fair value	$ (200)			$ (200)		331
Swap instrument two matures on December 17, 2021 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 100,000			$ 100,000		100,000
Fixed Rate Per annum	1.989%			1.989%
Expiration Date				Dec. 17, 2021
Fair value	$ (798)			$ (798)		1,318
Swap instrument three matures on December 17, 2021 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 75,000			$ 75,000		75,000
Fixed Rate Per annum	1.989%			1.989%
Expiration Date				Dec. 17, 2021
Fair value	$ (599)			$ (599)		990
Swap instrument one matures on April 27, 2022 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 50,000			$ 50,000		50,000
Fixed Rate Per annum	2.033%			2.033%
Expiration Date				Apr. 27, 2022
Fair value	$ (527)			$ (527)		667
Swap instrument two matures on April 27, 2022 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 100,000			$ 100,000		100,000
Fixed Rate Per annum	2.029%			2.029%
Expiration Date				Apr. 27, 2022
Fair value	$ (1,044)			$ (1,044)		1,341
Swap instrument three matures on April 27, 2022 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 50,000			$ 50,000		50,000
Fixed Rate Per annum	2.033%			2.033%
Expiration Date				Apr. 27, 2022
Fair value	$ (528)			$ (528)		666
Swap instrument one matures on December 17, 2023 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 100,000			$ 100,000		100,000
Fixed Rate Per annum	2.617%			2.617%
Expiration Date				Dec. 17, 2023
Fair value	$ (3,930)			$ (3,930)		(782)
Swap instrument one matures on April 27, 2024 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 100,000			$ 100,000		100,000
Fixed Rate Per annum	2.621%			2.621%
Expiration Date				Apr. 27, 2024
Fair value	$ (4,213)			$ (4,213)		(818)
Swap instrument two matures on December 17, 2023 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 200,000			$ 200,000		200,000
Fixed Rate Per annum	2.636%			2.636%
Expiration Date				Dec. 17, 2023
Fair value	$ (3,754)			$ (3,754)		(722)
Swap instrument two matures on April 27, 2024 \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative	$ 200,000			$ 200,000		200,000
Fixed Rate Per annum	2.642%			2.642%
Expiration Date				Apr. 27, 2024
Fair value	$ (3,583)			$ (3,583)		$ (648)