Basis of Presentation and Consolidation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 56,350	$ 36,463	$ 185,606	$ 35,688
Preferred stock issued		0	0
Net proceeds from stock issuance	$ 2,083
Silver Creek [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents		$ 400
Ownership interest percentage		56.00%	56.00%
Silver Creek [Member] | Series B Preferred Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Preferred stock issued	1,600,000	0
Preferred stock price per share	$ 1.35
Net proceeds from stock issuance	$ 2,100