Revenue Recognition - Summary of Disaggregation of Revenue According to Revenue Stream and Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	$ (10,642)	$ 9,793
Noninterest income	98,424	107,382
Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	47,000	41,957
Trading And Investment Banking
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	1,067	5,453
Noninterest income	1,723	5,581
Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	43	35
Noninterest income	25,081	21,281
Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	259	338
Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	9,860	7,243
Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	(8,157)	(8,061)
Noninterest income	16,545	17,067
Gains On Sales Of Securities Available For Sale, Net [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	1,227	809
Noninterest income	1,227	809
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue (Expense) out of Scope of ASC 606	(4,822)	11,557
Noninterest income	(3,271)	13,106
Commercial Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	22,339	22,336
Noninterest income	11,240	23,181
Commercial Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	6,892	7,461
Commercial Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	59	48
Commercial Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	14,988	14,488
Commercial Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	400	339
Institutional Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	60,277	49,180
Noninterest income	61,952	55,850
Institutional Banking [Member] | Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	31,262	26,689
Institutional Banking [Member] | Trading And Investment Banking
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	656	128
Institutional Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	15,607	11,077
Institutional Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	7,590	5,422
Institutional Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	4,724	5,525
Institutional Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	438	339
Personal Banking [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	26,450	26,073
Noninterest income	25,232	28,351
Personal Banking [Member] | Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	15,738	15,268
Personal Banking [Member] | Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	2,539	2,708
Personal Banking [Member] | Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	259	338
Personal Banking [Member] | Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	2,211	1,773
Personal Banking [Member] | Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	4,990	5,115
Personal Banking [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue Scope of ASC 606	$ 713	$ 871