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Retirement plans Plan assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Prohibited Investments	The plans hold no securities of Perma-Pipe International Holdings, Inc.
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%
Defined Benefit Plan, Fair Value of Plan Assets	$ 6,228	$ 5,883	$ 6,168
Defined Benefit Plan, Target Allocation Percentage	target asset allocations of 55% equities (with a range of 40% - 65%), 25% fixed income (with a range of 20% - 35%) and 20% Alternative Investments (with a range of 15% - 25%)
Defined Benefit Plan, actual gain (loss) on plan assets	$ 650	$ (25)
Net periodic benefit cost, expected long-term return on assets	8.00%	8.00%
Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	64.00%
Available-for-sale Securities, Equity Securities	$ 3,000	$ 3,062
Bonds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	33.00%
Available-for-sale Securities	$ 2,188	2,168
Money Market Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	3.00%
Money Market Funds, at Carrying Value	$ 306	351
Pension Plan Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Available-for-sale Securities	214	0
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Available-for-sale Securities	5,402	5,230
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Available-for-sale Securities, Equity Securities	520	302
Available-for-sale Securities	$ 826	$ 653