Income Taxes - Component of Income Taxes Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of income tax expense (benefit):
Currently payable (receivable)	$ 200	$ (200)	$ (100)
Deferred income tax expense (benefit)	400	(15,200)	(5,500)
Income tax expense (benefit)	$ 579	$ (15,361)	$ (5,634)