Significant Items Making up Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components Of Deferred Tax Assets And Liabilities [Abstract]
Allowances not currently deductible for tax purposes	$ 1,177	$ 2,844
Net operating loss carryforwards	56,989	64,741
Accrued and other	1,977	7,149
Deferred Tax Assets, Gross, Total	60,143	74,734
Less valuation allowance	(58,248)	(71,023)
Deferred Tax Assets, Net of Valuation Allowance, Total	1,895	3,711
Depreciation and amortization	(1,085)	(2,220)
Other	(810)	(1,491)
Deferred Tax Liabilities, Gross, Total	$ (1,895)	$ (3,711)