Revenue from Contracts with Customers - Summary of Sources of Noninterest Income that are Subject to Noted Accounting Guidance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Brokerage services income	$ 47,428	$ 48,922	$ 51,069
Other revenues from operations:
Total other income	2,088,444	2,061,679	1,856,000
Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	370,788	432,978	429,337
Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	601,884	572,608	537,585
ASU 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Brokerage services income	47,428	48,922	51,069
Other revenues from operations:
Merchant discount and credit card fees	102,472	107,042	105,953
Other	84,611	91,613	90,369
Total other income	1,207,183	1,253,163	1,214,313
ASU 2014-09 [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	370,788	432,978	429,337
ASU 2014-09 [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	601,884	572,608	537,585
ASU 2014-09 [Member] | Business Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	40,475	36,844	34,557
Total other income	90,612	97,565	96,889
ASU 2014-09 [Member] | Business Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	50,119	60,690	62,323
ASU 2014-09 [Member] | Business Banking [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	18	31	9
ASU 2014-09 [Member] | Commercial Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	45,528	52,161	52,051
Other	9,408	7,498	8,796
Total other income	148,098	153,666	158,171
ASU 2014-09 [Member] | Commercial Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	92,720	93,044	96,407
ASU 2014-09 [Member] | Commercial Banking [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	442	963	917
ASU 2014-09 [Member] | Commercial Real Estate [Member]
Other revenues from operations:
Merchant discount and credit card fees	2,221	2,516	2,213
Other	6,218	8,615	7,259
Total other income	18,691	20,959	19,342
ASU 2014-09 [Member] | Commercial Real Estate [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	10,252	9,828	9,870
ASU 2014-09 [Member] | Discretionary Portfolio [Member]
Other revenues from operations:
Other	1,625	1,776	1,738
Total other income	1,625	1,776	1,738
ASU 2014-09 [Member] | Residential Mortgage Banking [Member]
Other revenues from operations:
Other	4,732	3,492	3,814
Total other income	4,732	3,496	3,824
ASU 2014-09 [Member] | Residential Mortgage Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer		4	10
ASU 2014-09 [Member] | Retail Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	13,481	12,140	14,924
Other	20,813	36,144	38,529
Total other income	246,152	311,943	308,043
ASU 2014-09 [Member] | Retail Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	211,858	263,659	254,590
ASU 2014-09 [Member] | All Other [Member]
Disaggregation Of Revenue [Line Items]
Brokerage services income	47,428	48,922	51,069
Other revenues from operations:
Merchant discount and credit card fees	767	3,381	2,208
Other	41,815	34,088	30,233
Total other income	697,273	663,758	626,306
ASU 2014-09 [Member] | All Other [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	5,839	5,753	6,137
ASU 2014-09 [Member] | All Other [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	$ 601,424	$ 571,614	$ 536,659