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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Brokerage services income	$ 11,602	$ 12,077	$ 35,194	$ 37,031
Other revenues from operations:
Total other income	520,561	527,779	1,537,194	1,540,639
Total other income	520,561	527,779	1,537,194	1,540,639
Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	91,355	111,092	274,971	321,991
Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	149,937	143,915	450,570	421,083
ASU 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Brokerage services income	11,602	12,077	35,194	37,031
Other revenues from operations:
Merchant discount and credit card fees	25,654	28,190	73,876	82,016
Other	21,407	20,353	60,477	69,013
Total other income	299,955	315,627	895,088	931,134
Merchant discount and credit card fees	25,654	28,190	73,876	82,016
Other	21,407	20,353	60,477	69,013
Total other income	299,955	315,627	895,088	931,134
ASU 2014-09 [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	91,355	111,092	274,971	321,991
ASU 2014-09 [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	149,937	143,915	450,570	421,083
ASU 2014-09 [Member] | Business Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	10,533	9,692	29,023	28,469
Total other income	22,060	24,832	67,089	73,905
Merchant discount and credit card fees	10,533	9,692	29,023	28,469
Total other income	22,060	24,832	67,089	73,905
ASU 2014-09 [Member] | Business Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	11,527	15,131	38,048	45,415
ASU 2014-09 [Member] | Business Banking [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer		9	18	21
ASU 2014-09 [Member] | Commercial Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	10,785	13,409	32,992	38,630
Other	2,940	1,239	5,913	5,386
Total other income	36,542	38,317	108,834	114,427
Merchant discount and credit card fees	10,785	13,409	32,992	38,630
Other	2,940	1,239	5,913	5,386
Total other income	36,542	38,317	108,834	114,427
ASU 2014-09 [Member] | Commercial Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	22,816	23,427	69,487	69,731
ASU 2014-09 [Member] | Commercial Banking [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	1	242	442	680
ASU 2014-09 [Member] | Commercial Real Estate [Member]
Other revenues from operations:
Merchant discount and credit card fees	492	670	1,720	1,772
Other	929	1,372	2,960	5,840
Total other income	3,768	4,457	12,404	14,915
Merchant discount and credit card fees	492	670	1,720	1,772
Other	929	1,372	2,960	5,840
Total other income	3,768	4,457	12,404	14,915
ASU 2014-09 [Member] | Commercial Real Estate [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	2,347	2,415	7,724	7,303
ASU 2014-09 [Member] | Discretionary Portfolio [Member]
Other revenues from operations:
Other	205	503	1,212	1,545
Total other income	205	503	1,212	1,545
Other	205	503	1,212	1,545
Total other income	205	503	1,212	1,545
ASU 2014-09 [Member] | Residential Mortgage Banking [Member]
Other revenues from operations:
Other	1,127	816	3,101	2,913
Total other income	1,127	816	3,101	2,917
Other	1,127	816	3,101	2,913
Total other income	1,127	816	3,101	2,917
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
ASU 2014-09 [Member] | Retail Banking [Member]
Other revenues from operations:
Merchant discount and credit card fees	4,159	4,150	9,880	11,854
Other	5,994	9,347	15,142	27,170
Total other income	63,532	81,952	180,095	234,291
Merchant discount and credit card fees	4,159	4,150	9,880	11,854
Other	5,994	9,347	15,142	27,170
Total other income	63,532	81,952	180,095	234,291
ASU 2014-09 [Member] | Retail Banking [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	53,379	68,455	155,073	195,267
ASU 2014-09 [Member] | All Other [Member]
Disaggregation Of Revenue [Line Items]
Brokerage services income	11,602	12,077	35,194	37,031
Other revenues from operations:
Merchant discount and credit card fees	(315)	269	261	1,291
Other	10,212	7,076	32,149	26,159
Total other income	172,721	164,750	522,353	489,134
Merchant discount and credit card fees	(315)	269	261	1,291
Other	10,212	7,076	32,149	26,159
Total other income	172,721	164,750	522,353	489,134
ASU 2014-09 [Member] | All Other [Member] | Service Charges on Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	1,286	1,664	4,639	4,271
ASU 2014-09 [Member] | All Other [Member] | Trust Income [Member]
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	$ 149,936	$ 143,664	$ 450,110	$ 420,382