Investments In Securities and Fair Value (Schedule Of Gross Unrealized Gains And Losses And Amortized Cost For Securities) (Details) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Fixed maturities, available-for-sale, amortized cost	$ 83,968		$ 112,037
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	0	$ 482
Impairment amount for cost-method investments	0		0
Government obligations
Debt and Equity Securities, FV-NI [Line Items]
Fixed maturities, available-for-sale, amortized cost			24,026
Available-for-sale, at fair value, Gross Unrealized Gains			57
Available-for-sale, at fair value, Gross Unrealized Losses			0
Available-for-sale, at fair value, Estimated Fair Value			24,083
General obligations of U.S. states, territories and political subdivisions
Debt and Equity Securities, FV-NI [Line Items]
Fixed maturities, available-for-sale, amortized cost	17,274		17,391
Available-for-sale, at fair value, Gross Unrealized Gains	1,083		1,262
Available-for-sale, at fair value, Gross Unrealized Losses	0		0
Available-for-sale, at fair value, Estimated Fair Value	18,357		18,653
Special revenue issuer obligations of U.S. states, territories and political subdivisions
Debt and Equity Securities, FV-NI [Line Items]
Fixed maturities, available-for-sale, amortized cost	43,468		44,939
Available-for-sale, at fair value, Gross Unrealized Gains	2,900		3,270
Available-for-sale, at fair value, Gross Unrealized Losses	2		3
Available-for-sale, at fair value, Estimated Fair Value	$ 46,366		$ 48,206
Number of Special Revenue Bonds	50		50
Corporate debt securities
Debt and Equity Securities, FV-NI [Line Items]
Fixed maturities, available-for-sale, amortized cost	$ 23,226		$ 25,681
Available-for-sale, at fair value, Gross Unrealized Gains	1,050		1,114
Available-for-sale, at fair value, Gross Unrealized Losses	17		24
Available-for-sale, at fair value, Estimated Fair Value	24,259		26,771
Total fixed maturities
Debt and Equity Securities, FV-NI [Line Items]
Fixed maturities, available-for-sale, amortized cost	83,968		112,037
Available-for-sale, at fair value, Gross Unrealized Gains	5,033		5,703
Available-for-sale, at fair value, Gross Unrealized Losses	19		27
Available-for-sale, at fair value, Estimated Fair Value	$ 88,982		$ 117,713

Number of Special Revenue Bonds

No definition available.

Name:	itic_NumberofSpecialRevenueBonds
Namespace Prefix:	itic_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

No definition available.

+ Details

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

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

+ Details

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

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

No definition available.

+ Details

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

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

+ Details

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

- Definition

Loss recognized as a result of the initial and subsequent write-down of a long-lived asset's carrying amount to fair value.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2921-110230

+ Details

Name:	us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNetAvailableforsaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_SovereignDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=itic_IssuerObligationsUsStatesAndPoliticalSubdivisionsDebtSecuritiesSpecialRevenuesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: