INCOME TAXES - Reconciliation of Expected Income Tax Expense to Actual Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
INCOME TAXES
Computed expected income tax expense			$ 36,062	$ 29,318
State income taxes, net of federal tax benefit			4,633	3,296
Domestic production activities deduction			(3,036)	(2,345)
Stock option exercises			(866)	(2,807)
Exclusion of non-controlling interests			(106)	(2,334)
Adjustments and other differences			1,051	1,994
Income tax expense	$ 12,062	$ 8,194	$ 37,738	$ 27,122