QUARTERLY INFORMATION (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Class of Stock [Line Items]
Total revenue	$ 79,562	$ 74,004	$ 73,050	$ 68,485	$ 73,530	$ 65,660	$ 65,194	$ 61,927	$ 295,101	$ 266,311	$ 252,172
Total costs and expenses	71,828	68,115	70,986	68,187	67,697	61,859	63,704	63,648
Gross margin	45,653	40,933	39,831	37,054	42,831	36,755	36,417	33,302	163,471	149,305	144,579
Operating (loss) income	7,734	5,889	2,064	298	5,833	3,801	1,490	(1,721)	15,985	9,403	11,808
Net ( loss) income	6,947	5,090	985	(76)	4,346	2,049	1,254	(1,263)	12,946	6,386	6,639
Common Class A [Member]
Class of Stock [Line Items]
Net ( loss) income									10,729	5,282	5,483
Basic net ( loss) income per share (in dollars per share)	$ 0.44	$ 0.33	$ 0.06	$ (0.01)	$ 0.29	$ 0.14	$ 0.08	$ (0.08)	$ 0.84	$ 0.42	$ 0.44
Diluted net (loss) income per share (in dollars per share)	$ 0.42	$ 0.31	$ 0.06	$ (0.01)	$ 0.27	$ 0.13	$ 0.08	$ (0.08)	$ 0.79	$ 0.41	$ 0.42
Common Class B [Member]
Class of Stock [Line Items]
Net ( loss) income									$ 2,217	$ 1,104	$ 1,156
Basic net ( loss) income per share (in dollars per share)	$ 0.37	$ 0.27	$ 0.05	$ 0	$ 0.24	$ 0.11	$ 0.07	$ (0.07)	$ 0.70	$ 0.35	$ 0.37
Diluted net (loss) income per share (in dollars per share)	$ 0.36	$ 0.27	$ 0.05	$ 0	$ 0.23	$ 0.11	$ 0.07	$ (0.07)	$ 0.68	$ 0.34	$ 0.35