Summary of Quarterly Results of Operations (unaudited) - Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Loans:
Discount accretion	$ 1,751	$ 714	$ 1,677	$ 1,323	$ 1,780	$ 2,034	$ 2,566	$ 1,712
All other loan interest income	80,005	75,242	68,241	56,422	59,024	58,691	57,738	58,724
Total loan interest income	81,756	75,956	69,918	57,745	60,804	60,725	60,304	60,436	$ 285,375	$ 242,269	$ 233,721
Debt securities, dividends and interest bearing cash at banks	21,233	20,410	17,037	11,450	10,220	8,903	8,175	7,480
Total interest and dividend income	102,989	96,366	86,955	69,195	71,024	69,628	68,479	67,916	355,505	277,047	267,184
Interest expense	4,089	2,260	1,909	1,271	1,241	1,395	1,396	1,476	9,529	5,508	9,457
Net interest income	98,900	94,106	85,046	67,924	69,783	68,233	67,083	66,440	345,976	271,539	257,727
Provision for (benefit from reversal of) credit losses	4,245	3,795	2,100	8,330	980	(1,435)	(260)	(6,060)	18,470	(6,775)	42,813
Net interest income after provision for (benefit from) credit losses	94,655	90,311	82,946	59,594	68,803	69,668	67,343	72,500	327,506	278,314	214,914
Noninterest income	15,880	15,640	16,430	15,096	16,502	15,095	15,957	16,110	63,046	63,664	55,194
Total noninterest expense	59,469	54,465	56,264	46,447	46,679	45,807	44,171	41,618	216,645	178,275	182,758
Income before income taxes	51,066	51,486	43,112	28,243	38,626	38,956	39,129	46,992	173,907	163,703	87,350
Income tax expense	14,723	14,148	11,748	7,869	10,404	11,534	10,767	13,343	48,488	46,048	22,536
Net income	$ 36,343	$ 37,338	$ 31,364	$ 20,374	$ 28,222	$ 27,422	$ 28,362	$ 33,649	$ 125,419	$ 117,655	$ 64,814
Per common share:
Net income (diluted) (in USD per share)	$ 1.09	$ 1.12	$ 0.93	$ 0.67	$ 0.94	$ 0.92	$ 0.95	$ 1.13	$ 3.83	$ 3.94	$ 2.16
Dividends paid (in dollars per share)	$ 0.30	$ 0.30	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 1.20	$ 1.00	$ 0.88