Stock-Based Compensation - Information about Deferred Tax Benefits Recognized Related to Restricted Stock Awards, Paid Dividends and the Fair Value of Vested Restricted Stock (Detail) - Restricted Stock [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred tax benefits recognized	$ 319	$ 244	$ 603	$ 490
Tax benefits realized for restricted stock and paid dividends	1,186	924	1,239	985
Fair value of vested restricted stock	$ 4,319	$ 3,530	$ 5,599	$ 4,331