Investments In Securities Investments In Securities (Schedule of Variable Interest Entities) (Details) - Other investments $ in Thousands	Jun. 30, 2018 USD ($)
Variable Interest Entity [Line Items]
Carrying Value	$ 9,663
Estimated Fair Value	10,030
Maximum Potential Loss	18,675
Tax credit LPs
Variable Interest Entity [Line Items]
Carrying Value	628
Estimated Fair Value	628
Maximum Potential Loss	1,325
Real estate LLCs or LPs
Variable Interest Entity [Line Items]
Carrying Value	4,893
Estimated Fair Value	5,141
Maximum Potential Loss	7,950
Small business investment LPs
Variable Interest Entity [Line Items]
Carrying Value	4,142
Estimated Fair Value	4,261
Maximum Potential Loss	$ 9,400

Estimated fair value amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

No definition available.

+ Details

Name:	itic_VariableInterestEntityNonconsolidatedFairValueAmountAssets
Namespace Prefix:	itic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=77990344&loc=d3e5728-111685

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=77990344&loc=d3e5747-111685

+ Details

Name:	us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount
Namespace Prefix:	us-gaap_
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

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

- Definition

Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

+ Details

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

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=itic_VariableInterestEntityNotPrimaryBeneficiaryTaxCreditLpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=itic_VariableInterestEntityNotPrimaryBeneficiaryRealEstateLLCorLPMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=itic_VariableInterestEntityNotPrimaryBeneficiarySmallBusinessInvestmentLPMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: