Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2015
Net Investment Income [Line Items]
Held-to-maturity short-term investments	$ 24,929	$ 29,961	$ 24,929	$ 29,961	$ 69,845
Depreciation expense	$ 1,419	$ 1,543	$ 2,824	$ 3,037
Effective antidilutive securities excluded from computation of net income per share (in shares)	258	236	258	236
Commercial Paper [Member]
Net Investment Income [Line Items]
Held-to-maturity short-term investments	$ 24,929	$ 29,961	$ 24,929	$ 29,961	$ 69,845