Business Segments - Financial Information by Business Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Interest and dividend income	$ 711,516	$ 513,656	$ 484,967
Interest expense	230,178	39,343	27,034
NET INTEREST INCOME	481,338	474,313	457,933
Provision for credit losses	17,734	(1,663)	(64,274)
Net interest income after provision for credit losses	463,604	475,976	522,207
Non-interest income	120,447	117,391	132,785
Non-interest expense	390,002	356,966	353,143
Income before provision for income taxes	194,049	236,401	301,849
Provision for income taxes	35,017	44,288	59,589
Net income	159,032	192,113	242,260
Preferred stock dividends	10,125	10,125	10,125
Net income available to common shareholders	148,907	181,988	232,135
Community Banking [Member]
Segment Reporting Information [Line Items]
Interest and dividend income	711,516	513,656	484,967
Interest expense	230,178	39,343	27,034
NET INTEREST INCOME	481,338	474,313	457,933
Provision for credit losses	17,734	(1,663)	(64,274)
Net interest income after provision for credit losses	463,604	475,976	522,207
Non-interest income	92,312	89,840	103,274
Non-interest expense	370,771	340,573	336,766
Income before provision for income taxes	185,145	225,243	288,715
Provision for income taxes	33,147	41,945	56,831
Net income	151,998	183,298	231,884
Preferred stock dividends	10,125	10,125	10,125
Net income available to common shareholders	141,873	173,173	221,759
Trust and Investment Services [Member]
Segment Reporting Information [Line Items]
Non-interest income	28,135	27,551	29,511
Non-interest expense	19,231	16,393	16,377
Income before provision for income taxes	8,904	11,158	13,134
Provision for income taxes	1,870	2,343	2,758
Net income	7,034	8,815	10,376
Net income available to common shareholders	$ 7,034	$ 8,815	$ 10,376