Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Operating loss carryforwards used against taxable income	$ 4,400,000		$ 4,400,000
Expiration dates, operating loss carried forward			Dec. 31, 2027
Alternative minimum tax credits carried forward	2,200,000		$ 2,200,000
Retained earnings for which no provision made	21,100,000		21,100,000
Unrecorded deferred tax liability	4,400,000		4,400,000
Deficit tax earnings and profits	167,852,000		167,852,000	$ 152,675,000
Unrecognized tax benefits or accrued interest and penalties	0		$ 0	$ 0
Year under examination by taxing authorities			2014
Tax at statutory rate, rate			35.00%	35.00%	35.00%
Tax Cuts And Jobs Act Of 2017 Change In Tax Rate Income Tax Expense Benefit	1,500,000		$ 1,500,000
Scenario, Plan [Member]
Income Tax Disclosure [Line Items]
Tax at statutory rate, rate		21.00%
Home Savings [Member]
Income Tax Disclosure [Line Items]
Deficit tax earnings and profits	$ 17,600,000		$ 17,600,000