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Income Taxes - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Income Tax Disclosure [Abstract]          
Statutory federal corporate tax rate     35.00%    
Valuation allowance $ 1,700   $ 1,700   $ 1,900
Pre-tax loss 3,351 $ (327) 3,447 $ (39,306) $ (45,100)
DTA related to net operating loss carryforwards 22,700   $ 22,700    
DTA related to operating loss carryforwards expiration, description     do not expire until 2031 through 2036    
AMT carryforwards $ 2,100   $ 2,100