Revenue Recognition - Summary of Disaggregation of Revenue According to Revenue Stream and Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	$ 1,507	$ 5,731	$ 15,433	$ 70,981
Noninterest income	133,317	128,723	401,599	428,736
Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	66,668	59,586	190,616	178,000
Trading and Investment Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	3,653	5,425	13,448	17,772
Noninterest income	3,771	5,387	13,879	17,950
Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	26	33	68	153
Noninterest income	21,080	19,932	63,620	65,409
Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	272	375	771	879
Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	13,400	13,840	40,680	29,687
Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	(9,287)	(8,578)	(29,668)	(25,850)
Noninterest income	19,296	19,379	56,047	53,854
Investment Securities Gains (Losses), Net [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	271	(1,345)	(4,153)	58,853
Noninterest income	271	(1,345)	(4,153)	58,853
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	6,844	10,196	35,738	20,053
Noninterest income	8,559	11,569	40,139	24,104
Commercial Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	26,900	25,281	78,223	73,157
Noninterest income	23,091	16,785	71,658	100,379
Commercial Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	9,845	8,357	28,150	25,998
Commercial Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	69	66	197	174
Commercial Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	16,763	16,656	49,263	46,387
Commercial Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	223	202	613	598
Institutional Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	81,503	73,642	238,106	212,459
Noninterest income	86,521	89,386	257,573	243,740
Institutional Banking [Member] | Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	52,939	46,385	150,531	137,225
Institutional Banking [Member] | Trading and Investment Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	118	(38)	431	178
Institutional Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	9,917	9,564	30,815	33,704
Institutional Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	11,353	11,904	34,835	23,738
Institutional Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	6,337	5,350	19,677	16,234
Institutional Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	839	477	1,817	1,380
Personal Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	23,407	24,069	69,837	72,139
Noninterest income	23,705	22,552	72,368	84,617
Personal Banking [Member] | Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	13,729	13,201	40,085	40,775
Personal Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	1,292	1,978	4,587	5,554
Personal Banking [Member] | Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	272	375	771	879
Personal Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	1,978	1,870	5,648	5,775
Personal Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	5,483	5,951	16,775	17,083
Personal Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	$ 653	$ 694	$ 1,971	$ 2,073