Fair Value of Financial Instruments, Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial assets [Abstract]
Cash and cash equivalents	$ 619,187	$ 503,709
Securities available for sale	546,466	501,463
Held to maturity securities	22,283	22,924
Net loans	3,781,951	3,753,966
Accrued interest receivable	11,354	11,341
Financial liabilities [Abstract]
Demand deposits	408,417	405,069
Interest bearing deposits	3,998,861	3,859,444
Short-term borrowings	159,778	161,893
Accrued interest payable	1,472	1,024
Level 1 [Member]
Financial assets [Abstract]
Cash and cash equivalents	619,187	503,709
Securities available for sale	0	0
Held to maturity securities	0	0
Net loans	0	0
Accrued interest receivable	149	353
Financial liabilities [Abstract]
Demand deposits	408,417	405,069
Interest bearing deposits	2,583,471	2,594,672
Short-term borrowings	0	0
Accrued interest payable	176	104
Level 2 [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	0
Securities available for sale	546,466	501,463
Held to maturity securities	22,283	22,924
Net loans	0	0
Accrued interest receivable	2,214	2,371
Financial liabilities [Abstract]
Demand deposits	0	0
Interest bearing deposits	1,415,390	1,264,772
Short-term borrowings	159,778	161,893
Accrued interest payable	1,296	920
Level 3 [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	0
Securities available for sale	0	0
Held to maturity securities	0	0
Net loans	3,781,951	3,753,966
Accrued interest receivable	8,991	8,617
Financial liabilities [Abstract]
Demand deposits	0	0
Interest bearing deposits	0	0
Short-term borrowings	0	0
Accrued interest payable	0	0
Carrying Value [Member]
Financial assets [Abstract]
Cash and cash equivalents	619,187	503,709
Securities available for sale	546,466	501,463
Held to maturity securities	21,609	22,501
Federal Reserve Bank and Federal Home Loan Bank stock	8,953	8,953
Net loans	3,861,153	3,829,330
Accrued interest receivable	11,354	11,341
Financial liabilities [Abstract]
Demand deposits	408,417	405,069
Interest bearing deposits	4,004,652	3,869,178
Short-term borrowings	159,778	161,893
Accrued interest payable	$ 1,472	$ 1,024

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

No definition available.

Name:	trst_DebtSecuritiesHeldToMaturityFairValueDisclosures
Namespace Prefix:	trst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of money in accounts that may bear interest and that the depositor is entitled to withdraw at any time without prior notice.

+ References

No definition available.

+ Details

Name:	trst_DemandDepositAccountsFairValueDisclosure
Namespace Prefix:	trst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure. This item represents the aggregate of all interest bearing deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits among others.

+ References

No definition available.

+ Details

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Namespace Prefix:	trst_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents amount as of the balance sheet date of [accrued] interest payable on all forms of debt, including deposits and borrowings, that has been incurred and is unpaid.

+ References

No definition available.

+ Details

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

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents amount as of the balance sheet date of [accrued] interest receivable on loans, investment securities and federal funds sold and other short-term investments that has been earned and is unpaid.

+ References

No definition available.

+ Details

Name:	trst_InterestReceivableFairValueDisclosure
Namespace Prefix:	trst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount shown on an entity's books for investments in Federal Reserve Bank and Federal Home Loan Bank stock.

+ References

No definition available.

+ Details

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Namespace Prefix:	trst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

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

- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3044-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

- References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

+ Details

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

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

+ Details

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