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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
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Period Type:	instant

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.

No definition available.

Name:	us-gaap_ShortTermDebtLineItems
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Data Type:	xbrli:stringItemType
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Weighted average interest rate of short-term debt outstanding calculated at point in time.

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Name:	us-gaap_ShortTermDebtWeightedAverageInterestRate
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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, the maximum amount borrowed at any time during the period.

No definition available.

Name:	us-gaap_ShorttermDebtMaximumAmountOutstandingDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ShortTermDebtTypeAxis=tris_ShortTermBorrowingsOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_CreditFacilityAxis=tris_RevolvingCreditAgreement2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: