Debt instrument, additional mandatory prepayments percentage.

No definition available.

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- Definition

Debt Instrument, Covenant, Fair Market Value of Collateral, Percentage.

+ References

No definition available.

+ Details

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- Definition

Debt instrument covenant on collateral fair market value.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Debt instrument covenant percentage benchmark of aggregate fair market value of collateral vessels certain joint ventures equity interests.

+ References

No definition available.

+ Details

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- Definition

Debt instrument, covenant related to base amount available.

+ References

No definition available.

+ Details

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Namespace Prefix:	insw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Quarterly installment percentage of original principal amount for period one.

+ References

No definition available.

+ 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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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

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Balance Type:	credit
Period Type:	duration

- Details

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Balance Type:
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- Details

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- Details

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Debt (2017 Debt Facilities) (Narrative) (Details) $ in Thousands			1 Months Ended	9 Months Ended		12 Months Ended
	Oct. 08, 2019 USD ($)	Jun. 22, 2017 USD ($)	Jul. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Repayments of Other Long-term Debt				$ 10,000	$ 62,069
2017 Debt Facilities [Member]
Debt Instrument [Line Items]
Debt instrument covenant on collateral fair market value		$ 300,000
Debt instrument covenant percentage benchmark against certain fair market values		65.00%
Debt Instrument Covenant Fair Market Value Of Collateral Percentage				33.00%
Term Loan [Member] \| 2017 Debt Facilities [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 550,000
Quarterly installment percentage of original principal amount for period one				1.25%
Debt instrument, covenant related to base Available Amount				$ 12,147
Repayments of Other Long-term Debt			$ 10,000			$ 60,000
Debt instrument, additional mandatory prepayments, percentage				75
Term Loan [Member] \| 2017 Debt Facilities [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of Other Long-term Debt	$ 100,000