Basis of Presentation and Consolidation - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 56,350	$ 35,688	$ 100,323	$ 65,086
Preferred stock issued	0	0
Net proceeds from stock issuance	$ 2,083
Silver Creek Series B Preferred Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Preferred stock issued	1,600
Preferred stock price per share	$ 1.35
Net proceeds from stock issuance	$ 2,100
Silver Creek [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 1,200
Ownership interest percentage	56.00%	60.00%