Revenue Recognition - Summary of Non Interest Income, Segregated by Revenue Streams in-Scope and Out-of-Scope of Topic 606 (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Noninterest income:
Gain on OREO, net	$ 24		$ 129	$ 3,540
Other	2,603	$ 1,178	4,647	2,569
Total noninterest income	18,205	9,695	34,508	22,611
Service Charges on Deposit Accounts [Member]
Noninterest income:
Revenue from contract with customer	5,065	4,091	10,206	8,136
Trust and Investment Services [Member]
Noninterest income:
Revenue from contract with customer	2,452	2,399	4,634	4,556
Bankcard Services [Member]
Noninterest income:
Revenue from contract with customer	1,027	958	1,977	1,762
Accounting Standards Update 2014-09 [Member]
Noninterest income:
Gain on OREO, net	24	0	129	3,540
Other	2,603	1,178	4,647	2,569
Total noninterest income	11,171	8,626	21,593	20,563
Accounting Standards Update 2014-09 [Member] | Service Charges on Deposit Accounts [Member]
Noninterest income:
Revenue from contract with customer	5,065	4,091	10,206	8,136
Accounting Standards Update 2014-09 [Member] | Trust and Investment Services [Member]
Noninterest income:
Revenue from contract with customer	2,452	2,399	4,634	4,556
Accounting Standards Update 2014-09 [Member] | Bankcard Services [Member]
Noninterest income:
Revenue from contract with customer	1,027	958	1,977	1,762
Accounting Standards Update 2014-09 Not Adopted [Member]
Noninterest income:
Total noninterest income	$ 7,034	$ 1,069	$ 12,915	$ 2,048