Earnings Per Common Share and Share Awards Schedule of Weighted Average Grant Date Fair Value of Stock Awards Plans (Details) - $ / shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Weighted-average market price	$ 192.71	$ 93.87	$ 73.00
Weighted-average grant-date fair value	$ 55.40	$ 28.75	$ 31.16

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Weighted Average Grant Date Fair Value

No definition available.

Name:	itic_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
Namespace Prefix:	itic_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant