CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Gain (Loss)	Non-controlling Interests	Total
Balances at Jan. 31, 2015	$ 2,195	$ 109,663	$ 73,614		$ (10,520)	$ 174,952
Balances (in shares) at Jan. 31, 2015	14,631,201
Net income			36,345		13,859	50,204
Foreign currency translation gain (loss)				$ (565)		(565)
Acquisition of APC	$ 15	3,521				3,536
Acquisition of APC (in shares)	98,818
Exercise of stock options	$ 16	1,802				$ 1,818
Exercise of stock options (in shares)	106,450					106,000
Stock option vesting		2,374				$ 2,374
Excess tax benefit on exercised stock options		(86)				(86)
Cash dividends			(10,378)			(10,378)
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)
Exercise of stock options	$ 93	15,808				$ 15,901
Exercise of stock options (in shares)	621,750					622,000
Stock option vesting		2,344				$ 2,344
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
Exercise of stock options	$ 17	3,138				$ 3,155
Exercise of stock options (in shares)	109,500					110,000
Stock option vesting		4,651				$ 4,651
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