Non-interest Income and Expense - Components of Non Interest Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Income and Expenses [Abstract]
Base salaries, net of deferred loan origination costs	$ 18,754	$ 17,656	$ 53,654	$ 51,624
Incentive compensation	2,184	3,791	7,680	10,064
Benefits and other compensation costs	8,383	5,452	22,314	17,058
Total salaries and benefits expense	29,321	26,899	83,648	78,746
Occupancy	3,440	3,711	10,713	11,223
Data processing and software	3,561	3,411	10,585	10,114
Equipment	1,549	1,679	4,411	5,298
Intangible amortization	1,431	1,431	4,293	4,293
Advertising	869	1,358	2,065	4,222
ATM and POS network charges	1,314	1,343	3,897	3,936
Professional fees	955	999	2,399	2,895
Telecommunications	619	867	1,983	2,437
Regulatory assessments and insurance	538	94	993	1,095
Postage	118	438	691	1,063
Operational losses	154	228	559	679
Courier service	345	357	1,013	1,039
Gain on sale of foreclosed assets	0	(50)	(57)	(246)
Loss on disposal of fixed assets	22	2	37	82
Other miscellaneous expense	2,478	3,577	9,783	11,617
Total other non-interest expense	17,393	19,445	53,365	59,747
Total non-interest expense	$ 46,714	$ 46,344	$ 137,013	$ 138,493