Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2016
Net Investment Income [Line Items]
Held-to-maturity short-term investments	$ 0	$ 24,929	$ 0	$ 24,929	$ 59,806
Depreciation expense	$ 1,290	$ 1,419	$ 2,647	$ 2,824
Effective antidilutive securities excluded from computation of net income per share (in shares)	508	258	570,000	258,000
Commercial Paper [Member]
Net Investment Income [Line Items]
Held-to-maturity short-term investments		$ 24,929		$ 24,929	$ 59,806