Investment in Silver Creek - Schedule of Non-Controlling Interest in Subsidiary (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Minority Interest [Line Items]
Balance at the beginning of the period			$ (1,539)	$ 239
Net loss attributable to Silver Creek	$ 31	$ (207)	(1,160)	(600)
Balance at date of deconsolidation			(1,852)
Carrying value of non-controlling interest			1,852
Balance at the end of the period		$ (361)		$ (361)
Series C Preferred Stock [Member]
Minority Interest [Line Items]
Issuance of Silver Creek Series C preferred stock			$ 847