Summary of Unaudited Quarterly Results of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 50,433	$ 46,195	$ 44,345	$ 42,670	$ 43,674	$ 38,250	$ 37,417	$ 38,783	$ 183,643	$ 158,124	$ 126,375
Cost of product revenue	10,114	9,458	9,027	8,723	8,826	8,130	7,194	7,446	37,322	31,596	24,507
Other operating expenses	36,641	32,143	33,920	35,254	30,716	27,202	24,291	27,776	137,958	109,985
Other income (expense), net	84	57	31	(5)	8	325	(8)	(6)	167	319	1,023
Income (loss) before income tax provision	3,762	4,651	1,429	(1,312)	4,140	3,243	5,924	3,555	8,530	16,862	2,543
Income tax provision	140	258	370	411	398	559	455	436	1,179	1,848	1,048
Net income	$ 3,622	$ 4,393	$ 1,059	$ (1,723)	$ 3,742	$ 2,684	$ 5,469	$ 3,119	$ 7,351	$ 15,014	$ 1,495
Basic net income (loss) per share	$ 0.09	$ 0.11	$ 0.03	$ (0.04)	$ 0.10	$ 0.07	$ 0.14	$ 0.08	$ 0.19	$ 0.38	$ 0.04
Diluted net income (loss) per share	$ 0.09	$ 0.11	$ 0.03	$ (0.04)	$ 0.09	$ 0.07	$ 0.13	$ 0.08	$ 0.18	$ 0.37	$ 0.04