Segment Reporting - Schedule Of Segment Reporting Information, By Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net interest income	$ 429,827	$ 401,251	$ 411,264
(Release of) provision for loan losses	(9,686)	38,800	6,300
Release of allowance for loan losses	(9,686)
Net interest income after provision for loan losses	439,513	362,451	404,964
Noninterest income	193,155	178,373	182,299
Noninterest expense	443,956	504,923	412,684
Income before provision for income taxes	188,712	35,901	174,579
Tax (expense) or benefit	34,047	13,163	39,481
Net income	154,665	22,738	135,098
Total assets	23,512,128	15,964,190	11,628,775
Total liabilities	20,105,776	12,536,138	10,028,622
Eliminations and Reconciling Items
Segment Reporting Information [Line Items]
Net interest income	0	0	0
(Release of) provision for loan losses		0	0
Release of allowance for loan losses	0
Net interest income after provision for loan losses	0	0	0
Noninterest income	(389)	(700)	(246)
Noninterest expense	(4,234)	(4,588)	(3,682)
Income before provision for income taxes	3,845	3,888	3,436
Tax (expense) or benefit	0	0	0
Net income	3,845	3,888	3,436
Total assets	(69,161)	(67,201)	(52,307)
Total liabilities	(69,161)	(67,201)	(52,307)
Banking Business | Operating Segments
Segment Reporting Information [Line Items]
Net interest income	429,827	401,251	411,264
(Release of) provision for loan losses		38,800	6,300
Release of allowance for loan losses	(9,686)
Net interest income after provision for loan losses	439,513	362,451	404,964
Noninterest income	96,376	82,334	89,840
Noninterest expense	365,410	431,705	337,323
Income before provision for income taxes	170,479	13,080	157,481
Tax (expense) or benefit	29,994	7,870	35,542
Net income	140,485	5,210	121,939
Total assets	23,376,521	15,831,175	11,515,117
Total liabilities	20,125,218	12,547,838	10,046,189
Insurance Agency Business | Operating Segments
Segment Reporting Information [Line Items]
Net interest income	0	0	0
(Release of) provision for loan losses		0	0
Release of allowance for loan losses	0
Net interest income after provision for loan losses	0	0	0
Noninterest income	97,168	96,739	92,705
Noninterest expense	82,780	77,806	79,043
Income before provision for income taxes	14,388	18,933	13,662
Tax (expense) or benefit	4,053	5,293	3,939
Net income	10,335	13,640	9,723
Total assets	204,768	200,216	165,965
Total liabilities	$ 49,719	$ 55,501	$ 34,740