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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	$ 55,340	$ 25,929	$ 65,250	$ 30,438
Noninterest income	176,335	131,589	300,013	240,486
Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	58,886	53,863	118,414	108,697
Trading and Investment Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	7,063	8,350	12,347	17,405
Noninterest income	7,123	8,670	12,563	18,026
Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	50	78	120	148
Noninterest income	20,835	22,592	45,477	44,568
Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	245	245	504	665
Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	12,391	2,592	15,847	5,926
Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	(9,383)	(8,810)	(17,272)	(16,426)
Noninterest income	17,840	16,063	34,475	30,736
Investment Securities Gains, Net [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	60,720	15,455	60,198	7,119
Noninterest income	60,720	15,455	60,198	7,119
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	(3,110)	10,856	9,857	22,192
Noninterest income	(1,705)	12,109	12,535	24,749
Commercial Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	24,760	23,318	47,876	44,053
Noninterest income	56,894	37,106	83,594	45,281
Commercial Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	8,696	8,606	17,641	16,510
Commercial Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	75	10	108	74
Commercial Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	15,757	14,499	29,731	27,035
Commercial Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	232	203	396	434
Institutional Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	72,047	58,725	138,817	115,623
Noninterest income	81,082	68,745	154,354	137,166
Institutional Banking [Member] | Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	45,355	40,118	90,840	77,603
Institutional Banking [Member] | Trading and Investment Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	60	320	216	621
Institutional Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	10,250	12,432	24,140	25,009
Institutional Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	10,350	673	11,834	1,992
Institutional Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	5,553	4,771	10,884	9,583
Institutional Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	479	411	903	815
Personal Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	24,188	23,617	48,070	50,372
Noninterest income	38,359	25,738	62,065	58,039
Personal Banking [Member] | Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	13,531	13,745	27,574	31,094
Personal Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	1,839	1,476	3,576	2,901
Personal Banking [Member] | Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	245	245	504	665
Personal Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	1,966	1,909	3,905	3,860
Personal Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	5,913	5,603	11,132	10,544
Personal Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	$ 694	$ 639	$ 1,379	$ 1,308