Summary of Unaudited Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2016	Mar. 31, 2015		Mar. 31, 2014
Disclosure Unaudited Quarterly Financial Information [Abstract]
Total revenues	$ 93,957	$ 85,795	$ 76,359	$ 73,432	$ 67,557		$ 62,005		$ 51,938		$ 48,811		$ 329,543	$ 230,311		$ 183,643
Cost of product revenue	14,663	12,744	12,144	10,868	10,806		9,838		9,612		9,689		50,419	39,945		37,322
Other operating expenses	59,481	55,608	51,398	47,533	44,388		38,504		38,148		40,660		214,020	161,700
Other income (expense), net	414	55	149	116	9		38		(3)		55		734	99		167
Income before income taxes	20,227	17,498	12,966	15,147	12,372		13,701		4,175		(1,483)		65,838	28,765		8,530
Income tax (benefit) provision	9,229	6,943	5,231	6,288	(86,502)	[1]	1,017	[1]	336	[1]	226	[1]	27,691	(84,923)	[1]	1,179
Net income	$ 10,998	$ 10,555	$ 7,735	$ 8,859	$ 98,874		$ 12,684		$ 3,839		$ (1,709)		$ 38,147	$ 113,688		$ 7,351
Basic net income (loss) per share	$ 0.26	$ 0.25	$ 0.18	$ 0.21	$ 2.40		$ 0.31		$ 0.09		$ (0.04)		$ 0.90	$ 2.80		$ 0.19
Diluted net income (loss) per share	$ 0.24	$ 0.23	$ 0.17	$ 0.20	$ 2.24		$ 0.30		$ 0.09		$ (0.04)		$ 0.85	$ 2.65		$ 0.18

[1] Income tax benefit for the quarter and year ended March 31, 2015 were impacted by the release of the $101.5 million valuation allowance on certain deferred tax assets.