Share Repurchase Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Share Repurchase Plan, shares repurchased during period, shares	185,072	0	150,000
Shares Repurchase Plan, shares repurchased during period, cost	$ 4.0		$ 3.6
Shares available to be repurchased under the plan	679,174