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, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Brokerage services income	$ 48,922	$ 51,069	$ 61,445
Other revenues from operations:
Total other income	2,061,679	1,856,000	1,851,143
Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	432,978	429,337	427,372
Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	572,608	537,585	$ 501,381
ASU 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Brokerage services income	48,922	51,069
Other revenues from operations:
Merchant discount and credit card fees	107,042	105,953
Other	91,613	90,369
Total other income	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	432,978	429,337
ASU 2014-09 [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	572,608	537,585
ASU 2014-09 [Member] | Business Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	36,844	34,557
Total other income	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	60,690	62,323
ASU 2014-09 [Member] | Business Banking [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	31	9
ASU 2014-09 [Member] | Commercial Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	52,161	52,051
Other	7,498	8,796
Total other income	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	93,044	96,407
ASU 2014-09 [Member] | Commercial Banking [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	963	917
ASU 2014-09 [Member] | Commercial Real Estate [Member]
Other revenues from operations:
Merchant discount and credit card fees	2,516	2,213
Other	8,615	7,259
Total other income	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	9,828	9,870
ASU 2014-09 [Member] | Discretionary Portfolio [Member]
Other revenues from operations:
Other	1,776	1,738
Total other income	1,776	1,738
ASU 2014-09 [Member] | Residential Mortgage Banking [Member]
Other revenues from operations:
Other	3,492	3,814
Total other income	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	12,140	14,924
Other	36,144	38,529
Total other income	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	263,659	254,590
ASU 2014-09 [Member] | All Other [Member]
Disaggregation Of Revenue [Line Items]
Brokerage services income	48,922	51,069
Other revenues from operations:
Merchant discount and credit card fees	3,381	2,208
Other	34,088	30,233
Total other income	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	5,753	6,137
ASU 2014-09 [Member] | All Other [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	$ 571,614	$ 536,659