Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes Disclosure [Line Items]
Deferred tax assets, valuation allowance	$ 54,829,000	$ 72,380,000	$ 54,829,000
Tax reform deferred rate change	28,163,000		28,163,000
Foreign investments benefit		0	0
Decreased income tax benefit		271,000	8,569,000
Net operating loss carryforwards	$ 59,536,000	88,341,000	$ 59,536,000
Net operating losses carry forwards, expiration year			2037	2036
Uncertain tax positions		0
Tax Years 2012 Through 2014
Income Taxes Disclosure [Line Items]
Income tax refund claimed		$ 2,107,000