CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Gain	Non-controlling Interests	Total
Balances at Jan. 31, 2016	$ 2,226	$ 117,274	$ 99,581	$ (565)	$ 3,339	$ 221,855
Balances (in shares) at Jan. 31, 2016	14,836,469
Net income			70,328		7,098	77,426
Foreign currency translation gain (loss)				(197)		(197)
Stock compensation expense		2,344				2,344
Exercise of stock options	$ 93	15,808				$ 15,901
Exercise of stock options (in shares)	621,750					622,000
Cash distributions to joint venture partner					(9,500)	$ (9,500)
Cash dividends			(15,260)			(15,260)
Balances at Jan. 31, 2017	$ 2,319	135,426	154,649	(762)	937	292,569
Balances (in shares) at Jan. 31, 2017	15,458,219
Net income			72,011		335	72,346
Foreign currency translation gain (loss)				2,184		2,184
Stock compensation expense		4,651				4,651
Exercise of stock options	$ 17	3,138				$ 3,155
Exercise of stock options (in shares)	109,500					110,000
Cash distributions to joint venture partner					(1,229)	$ (1,229)
Cash dividends			(15,548)			(15,548)
Balances at Jan. 31, 2018	$ 2,336	143,215	211,112	1,422	43	358,128
Balances (in shares) at Jan. 31, 2018	15,567,719
Net income			52,036		(167)	51,869
Foreign currency translation gain (loss)				(1,768)		(1,768)
Stock compensation expense		1,645				1,645
Exercise of stock options	$ 1	101				$ 102
Exercise of stock options (in shares)	6,150					6,000
Cash distributions to joint venture partner					(72)	$ (72)
Cash dividends			(15,570)			(15,570)
Adoption of ASC Topic 606 | Impact of the Adoption of ASC Topic 606			38			38
Balances at Jan. 31, 2019	$ 2,337	$ 144,961	$ 247,616	$ (346)	$ (196)	$ 394,372
Balances (in shares) at Jan. 31, 2019	15,573,869