Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2015
Net Investment Income [Line Items]
Held-to-maturity short-term investments			$ 59,735	$ 39,802	$ 59,735	$ 39,802	$ 69,845
Depreciation expense			$ 1,389	$ 1,463	$ 4,213	$ 4,500
Effective antidilutive securities excluded from computation of net income per share (in shares)			387	223	253	223
Commercial Paper [Member]
Net Investment Income [Line Items]
Held-to-maturity short-term investments			$ 59,735	$ 39,802	$ 59,735	$ 39,802	$ 69,845
Commercial Paper [Member] | Forecast [Member]
Net Investment Income [Line Items]
Held-to-maturity securities, matured	$ 34,767	$ 24,968