Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2015	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2015	Sep. 01, 2020	Apr. 18, 2019
Class of Stock [Line Items]
Preferred Stock, shares outstanding		0	0	0
Repurchase of shares		1,100,000	1,100,000
Outstanding common stock at an average price paid per Share		$ 21.54	$ 21.54
Tax benefit in connection with stock compensation expense					$ 224
Employee stock loan amount		$ 43	$ 77
Employee stock loan maturity date		Mar. 31, 2021
Employee stock loan interest rate		1.60%
Reclassification adjustment for net gains included in net income		$ 0	0	$ 0
Reclassification adjustment of accretion expense to taxable interest income on securities		$ 509	$ 903	$ 453
Additional Repurchase [Member]
Class of Stock [Line Items]
Repurchase of shares		313,231
Outstanding common stock at an average price paid per Share		$ 20.82
Maximum [Member]
Class of Stock [Line Items]
Number of shares authorized to be repurchased							1,100,000
Maximum [Member] | Additional Repurchase [Member]
Class of Stock [Line Items]
Number of shares authorized to be repurchased						800,000
Class A Common Stock [Member]
Class of Stock [Line Items]
Number of common stock shares authorized		45,000,000
Shares issued, par value		$ 0.01
Shares issued to employees	203,216
Class B Common Stock [Member]
Class of Stock [Line Items]
Number of common stock shares authorized		5,000,000
Shares issued, par value		$ 0.01