QUARTERLY INFORMATION (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Class of Stock [Line Items]
Total revenue	$ 65,786	$ 61,709	$ 60,969	$ 63,708	$ 65,165	$ 60,733	$ 61,957	$ 59,403	$ 252,172	$ 247,258	$ 220,012
Total costs and expenses	62,570	58,629	59,411	59,754	58,842	56,435	57,310	56,779
Gross margin	38,362	35,178	33,950	37,089	38,887	34,578	35,145	33,309	144,579	141,919	126,064
Operating income	3,216	3,080	1,558	3,954	6,323	4,298	4,647	2,624	11,808	17,892	6,591
Net income	2,011	1,825	959	1,844	3,684	3,010	3,070	1,020	6,639	10,784	2,711
Common Class A [Member]
Class of Stock [Line Items]
Net income									5,483	8,935	2,244
Basic net income per share (in dollars per share)	$ 0.13	$ 0.12	$ 0.06	$ 0.12	$ 0.24	$ 0.19	$ 0.20	$ 0.07	$ 0.44	$ 0.69	$ 0.18
Diluted net income per share (in dollars per share)	$ 0.13	$ 0.12	$ 0.06	$ 0.12	$ 0.23	$ 0.19	$ 0.19	$ 0.06	$ 0.42	$ 0.67	$ 0.17
Common Class B [Member]
Class of Stock [Line Items]
Net income									$ 1,156	$ 1,849	$ 467
Basic net income per share (in dollars per share)	$ 0.11	$ 0.10	$ 0.05	$ 0.10	$ 0.20	$ 0.16	$ 0.16	$ 0.06	$ 0.37	$ 0.58	$ 0.15
Diluted net income per share (in dollars per share)	$ 0.11	$ 0.10	$ 0.05	$ 0.10	$ 0.19	$ 0.15	$ 0.16	$ 0.05	$ 0.35	$ 0.56	$ 0.14