Revenue from Contracts with Customers - Summary of Sources of Noninterest Income that are Subject to Noted Accounting Guidance (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation Of Revenue [Line Items]
Brokerage services income	$ 13,113	$ 13,129
Other revenues from operations:
Total other income	505,598	529,360
Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	92,777	106,161
Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	156,022	148,751
ASU 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Brokerage services income	13,113	13,129
Other revenues from operations:
Merchant discount and credit card fees	24,363	27,167
Other	22,910	23,306
Total other income	309,185	318,514
ASU 2014-09 [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	92,777	106,161
ASU 2014-09 [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	156,022	148,751
ASU 2014-09 [Member] | Business Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	9,481	10,331
Total other income	21,978	25,593
ASU 2014-09 [Member] | Business Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	12,497	15,250
ASU 2014-09 [Member] | Business Banking [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer		12
ASU 2014-09 [Member] | Commercial Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	10,407	13,316
Other	958	2,186
Total other income	35,660	39,963
ASU 2014-09 [Member] | Commercial Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	24,295	24,157
ASU 2014-09 [Member] | Commercial Banking [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer		304
ASU 2014-09 [Member] | Commercial Real Estate [Member]
Other revenues from operations:
Merchant discount and credit card fees	445	849
Other	1,091	843
Total other income	4,429	4,504
ASU 2014-09 [Member] | Commercial Real Estate [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	2,893	2,812
ASU 2014-09 [Member] | Discretionary Portfolio [Member]
Other revenues from operations:
Other	384	857
Total other income	384	857
ASU 2014-09 [Member] | Residential Mortgage Banking [Member]
Other revenues from operations:
Other	1,722	922
Total other income	1,722	922
ASU 2014-09 [Member] | Retail Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	3,921	2,271
Other	5,807	5,982
Total other income	61,180	69,923
ASU 2014-09 [Member] | Retail Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	51,452	61,670
ASU 2014-09 [Member] | All Other [Member]
Disaggregation Of Revenue [Line Items]
Brokerage services income	13,113	13,129
Other revenues from operations:
Merchant discount and credit card fees	109	400
Other	12,948	12,516
Total other income	183,832	176,752
ASU 2014-09 [Member] | All Other [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	1,640	2,272
ASU 2014-09 [Member] | All Other [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	$ 156,022	$ 148,435