QUARTERLY INFORMATION (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Class of Stock [Line Items]
Total revenue	$ 73,530	$ 65,660	$ 65,194	$ 61,927	$ 65,786	$ 61,709	$ 60,969	$ 63,708	$ 266,311	$ 252,172	$ 247,258
Total costs and expenses	67,697	61,859	63,704	63,648	62,570	58,629	59,411	59,754
Gross margin	42,831	36,755	36,417	33,302	38,362	35,178	33,950	37,089	149,305	144,579	141,919
Operating income (loss)	5,833	3,801	1,490	(1,721)	3,216	3,080	1,558	3,954	9,403	11,808	17,892
Net income	4,346	2,049	1,254	(1,263)	2,011	1,825	959	1,844	6,386	6,639	10,784
Common Class A [Member]
Class of Stock [Line Items]
Net income									5,282	5,483	8,935
Basic net income per common share (in dollars per share)	$ 0.29	$ 0.14	$ 0.08	$ (0.08)	$ 0.13	$ 0.12	$ 0.06	$ 0.12	$ 0.42	$ 0.44	$ 0.69
Diluted net income per common share (in dollars per share)	$ 0.27	$ 0.13	$ 0.08	$ (0.08)	$ 0.13	$ 0.12	$ 0.06	$ 0.12	$ 0.41	$ 0.42	$ 0.67
Common Class B [Member]
Class of Stock [Line Items]
Net income									$ 1,104	$ 1,156	$ 1,849
Basic net income per common share (in dollars per share)	$ 0.24	$ 0.11	$ 0.07	$ (0.07)	$ 0.11	$ 0.10	$ 0.05	$ 0.10	$ 0.35	$ 0.37	$ 0.58
Diluted net income per common share (in dollars per share)	$ 0.23	$ 0.11	$ 0.07	$ (0.07)	$ 0.11	$ 0.10	$ 0.05	$ 0.10	$ 0.34	$ 0.35	$ 0.56