Debt instrument prepayment fee amount.

No definition available.

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

- 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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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

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-Topic 835
-SubTopic 30
-Section 45
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Balance Type:	debit
Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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

- 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

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of income (expense) related to nonoperating activities, classified as other.

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Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for loan and debt issuance costs.

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+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

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Balance Type:	debit
Period Type:	duration

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DEBT (Debt Modification, Repurchases and Extinguishment) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Jan. 28, 2020	Jan. 23, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Interest Expense		$ 7,155	$ 11,172
Gain (Loss) on extinguishment of debt	$ (992)
Other (expense)/income	(13,432)		1,036
Amortization of Issuance, Deferred Financing Costs, Commitments, Administrative and Other Fees for Debt Facilities [Member]
Debt Instrument [Line Items]
Interest Expense	11,852		17,226
2017 Debt Facilities [Member]
Debt Instrument [Line Items]
Other (expense)/income	(13,493)
2017 Term Loan, ABN Term Loan Facility and 10.75% Subordinated Notes [Member]
Debt Instrument [Line Items]
Write off of deferred debt issuance cost	12,501
2020 Debt Facilities [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross	7,329
Core Revolving Facility [Member]
Debt Instrument [Line Items]
Long-term line of credit				$ 20,000
Core Term Loan Facility and Transition Term Loan Facility [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross	6,345
Payments of financing costs	6,577
Core Term Loan Facility and Transition Term Loan Facility Deemed Expensed [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross			$ 232
10.75% Subordinated Notes [Member]
Debt Instrument [Line Items]
Debt instrument, repurchase amount				$ 27,931
Revolving Credit Facility [Member] \| INSW Facilities [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross						$ 274
Revolving Credit Facility [Member] \| Core Revolving Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					$ 40,000
Deferred finance costs, gross	980
Secured Debt [Member] \| 2020 Debt Facilities [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					390,000
Term Loan [Member] \| Core Term Loan Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					300,000
Term Loan [Member] \| Core Revolving Facility [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross	752
Term Loan [Member] \| Transition Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					$ 50,000
Subordinated Debt [Member] \| 10.75% Subordinated Notes [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee amount	$ 992