Revenue Recognition - Summary of Disaggregation of Revenue According to Revenue Stream and Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	$ 10,627	$ 55,340	$ 13,926	$ 65,250
Noninterest income	138,082	176,335	268,282	300,013
Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	61,589	58,886	123,948	118,414
Trading and Investment Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	4,645	7,063	9,795	12,347
Noninterest income	4,800	7,123	10,108	12,563
Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	24	50	42	120
Noninterest income	21,381	20,835	42,540	45,477
Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	225	245	499	504
Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	13,604	12,391	27,280	15,847
Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	(10,649)	(9,383)	(20,381)	(17,272)
Noninterest income	18,579	17,840	36,751	34,475
Investment Securities Gains (Losses), Net [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	900	60,720	(4,424)	60,198
Noninterest income	900	60,720	(4,424)	60,198
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	15,707	(3,110)	28,894	9,857
Noninterest income	17,004	(1,705)	31,580	12,535
Commercial Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	26,876	24,760	51,323	47,876
Noninterest income	25,666	56,894	48,568	83,594
Commercial Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	9,778	8,696	18,305	17,641
Commercial Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	65	75	128	108
Commercial Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	16,868	15,757	32,500	29,731
Commercial Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	165	232	390	396
Institutional Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	77,596	72,047	156,603	138,817
Noninterest income	86,813	81,082	171,051	154,354
Institutional Banking [Member] | Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	48,413	45,355	97,592	90,840
Institutional Banking [Member] | Trading and Investment Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	155	60	313	216
Institutional Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	10,159	10,250	20,898	24,140
Institutional Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	11,687	10,350	23,482	11,834
Institutional Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	6,662	5,553	13,340	10,884
Institutional Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	520	479	978	903
Personal Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	22,983	24,188	46,430	48,070
Noninterest income	25,603	38,359	48,663	62,065
Personal Banking [Member] | Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	13,176	13,531	26,356	27,574
Personal Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	1,420	1,839	3,295	3,576
Personal Banking [Member] | Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	225	245	499	504
Personal Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	1,852	1,966	3,670	3,905
Personal Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	5,698	5,913	11,292	11,132
Personal Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	$ 612	$ 694	$ 1,318	$ 1,379