INCOME TAXES - Reconciliation of Expected Income Tax Expense to Actual Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
INCOME TAXES
Computed "expected" income tax expense	$ 40,086	$ 26,427	$ 22,528
State income taxes, net of federal benefit	4,001	4,030	3,284
Stock option exercises	(4,969)
Domestic production activities deduction	(2,906)	(1,635)	(1,504)
Exclusion of noncontrolling interests	(2,484)	(4,823)	(4,582)
Other permanent differences	1,933	1,557	902
Adjustments and other differences	1,445	(254)	284
Income tax expense	$ 37,106	$ 25,302	$ 20,912