Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	$ 3,724,148	$ 3,600,892
Held-to-maturity, Fair Value	3,301,284	3,380,624
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	3,833,043	3,860,235
Equity Securities, FV-NI and without Readily Determinable Fair Value	19,571	41,651
FHLB and Federal Reserve Bank stocks	173,968	229,171
Assets	41,137,084	41,015,855
Liabilities, Fair Value Disclosure
Noninterest-bearing Domestic Deposit, Demand	6,254,135	6,119,956
Deposits	33,713,158	33,446,049
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	265,671	326,780
Bank Term Funding Program Funding	500,000	0
Short-Term Debt	765,671	326,780
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	1,333,411	1,940,194
Liabilities	36,968,412	36,841,882
Standby letters of credit(c)
Liabilities, Fair Value Disclosure
Lending Related Commitments By Type [Domain]	230,396	212,029
Interest Rate Contract
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	40,812	32,985
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	10,709	533
Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Cash and Due from Banks	429,859	484,384
Interest-bearing Deposits in Banks and Other Financial Institutions	420,114	425,089
Federal funds sold and securities purchased under agreements to resell	1,610	14,350
Equity Securities, FV-NI	7,071	31,651
Equity Securities, FV-NI and without Readily Determinable Fair Value	19,571	41,651
FHLB and Federal Reserve Bank stocks	173,968	229,171
Residential Held-for-sale, Fair Value Disclosure	52,414	33,011
Loan, Held-for-Sale, Fair Value Disclosure		90,303
Loans and Leases Receivable, Net Amount	29,138,257	28,865,124
Loans Receivable, Fair Value Disclosure	27,739,448	27,371,086
Bank and corporate owned life insurance	685,089	682,649
Servicing Asset	85,226	84,390
Assets, Fair Value Disclosure	36,754,723	36,561,249
Assets	38,685,290	38,534,897
Liabilities, Fair Value Disclosure
Noninterest-bearing Domestic Deposit, Demand	6,254,135	6,119,956
Deposits, Savings Deposits	5,124,639	4,835,701
Interest-Bearing Domestic Deposit, Demand	8,747,127	8,843,967
Deposits, Money Market Deposits	6,721,674	6,330,453
Brokered cds and other time deposits	3,931,230	4,447,479
Brokered cds and other time deposits fair value	3,931,230	4,447,479
Time Deposits, at Carrying Value	2,934,352	2,868,494
Time Deposits	2,934,352	2,868,494
Deposits	33,713,158	33,446,049
Federal Funds Purchased and Securities Loaned or Sold under Agreements to Repurchase, Fair Value Disclosure	265,661	326,757
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	265,671	326,780
Bank Term Funding Program Funding, Fair Value Disclosure	497,959
Bank Term Funding Program Funding	500,000
Short-Term Debt	765,671
Short-term Debt, Fair Value	763,620
Federal Home Loan Bank Borrowings, Fair Value Disclosure	1,320,280	1,944,600
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	1,333,411	1,940,194
Other long-term funding	536,055	541,269
Long-term Debt, Fair Value	517,009	534,983
Repayments of Lines of Credit	2,347	2,157
Liabilities, Fair Value Disclosure	36,554,811	36,457,504
Liabilities	36,589,039	36,459,407
Fair Value, Measurements, Recurring | Commitments [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	222	673
Fair Value, Measurements, Recurring | Interest Rate Lock Commitments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	666	439
Fair Value, Measurements, Recurring | Designated as Hedging Instrument
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	2,164	8,075
Foreign Currency Contract, Asset, Fair Value Disclosure	624	632
Fair Value, Measurements, Recurring | Designated as Hedging Instrument | Interest Rate Contract
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	10,685	930
Fair Value, Measurements, Recurring | Designated as Hedging Instrument | Foreign Exchange Forward [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	230	2,946
Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	113,337	111,623
Foreign Currency Contract, Asset, Fair Value Disclosure	5,276	2,954
Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Interest Rate Contract
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	222,303	195,662
Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	4,956	2,746
US Treasury Securities
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	35,558	35,902
Held-to-maturity, Fair Value	969	963
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	999	999
US Treasury Securities | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	35,558	35,902
Held-to-maturity, Fair Value	969	963
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	999	999
US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	80,830	91,817
Held-to-maturity, Fair Value	1,523,734	1,554,059
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	1,676,275	1,682,473
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	80,830	91,817
Held-to-maturity, Fair Value	1,523,658	1,553,984
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	1,676,199	1,682,398
Residential Related Securities | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	1,090,998	1,120,794
Held-to-maturity, Fair Value	771,944	804,393
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	930,148	941,973
Residential Related Securities | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	2,214,513	2,042,675
Held-to-maturity, Fair Value	44,457	46,170
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	48,043	48,979
Residential Related Securities | Fair Value, Measurements, Recurring | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	1,090,998	1,120,794
Held-to-maturity, Fair Value	771,944	804,393
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	930,148	941,973
Residential Related Securities | Fair Value, Measurements, Recurring | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	2,214,513	2,042,675
Held-to-maturity, Fair Value	44,457	46,170
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	48,043	48,979
Residential Related Securities | Fair Value, Measurements, Recurring | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity, Fair Value	281,069	289,507
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	341,153	345,083
Commercial mortgage-related securities | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	17,008	16,937
Held-to-maturity, Fair Value	628,928	632,914
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	779,310	780,995
Commercial mortgage-related securities | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	152,232	154,793
Held-to-maturity, Fair Value	50,183	52,619
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	57,114	59,733
Commercial mortgage-related securities | Fair Value, Measurements, Recurring | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	17,008	16,937
Held-to-maturity, Fair Value	628,928	632,914
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	779,310	780,995
Commercial mortgage-related securities | Fair Value, Measurements, Recurring | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	152,232	154,793
Held-to-maturity, Fair Value	50,183	52,619
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	57,114	59,733
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	129,154	133,975
Held-to-maturity, Fair Value	0
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	129,154	133,975
US Government-sponsored Enterprises Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	890	1,051
Held-to-maturity, Fair Value	0
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	890	1,051
Other Debt Obligations | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	2,965	2,950
Available-for-sale Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	3,724,148	3,600,892
Held-to-maturity Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity, Fair Value	3,301,209	3,380,550
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	3,832,967	3,860,160
Fair Value, Inputs, Level 1
Assets, Fair Value Disclosure [Abstract]
Cash and Due from Banks	429,859	484,384
Interest-bearing Deposits in Banks and Other Financial Institutions	420,114	425,089
Federal funds sold and securities purchased under agreements to resell	1,610	14,350
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Cash and Due from Banks	429,859	484,384
Interest-bearing Deposits in Banks and Other Financial Institutions	420,114	425,089
Federal funds sold and securities purchased under agreements to resell	1,610	14,350
Equity Securities, FV-NI	6,966	6,883
FHLB and Federal Reserve Bank stocks	0	0
Residential Held-for-sale, Fair Value Disclosure	0	0
Loan, Held-for-Sale, Fair Value Disclosure		0
Loans Receivable, Fair Value Disclosure	0	0
Bank and corporate owned life insurance	0	0
Servicing Asset	0	0
Assets, Fair Value Disclosure	895,077	967,570
Liabilities, Fair Value Disclosure
Noninterest-bearing Domestic Deposit, Demand	0	0
Deposits, Savings Deposits	0	0
Interest-Bearing Domestic Deposit, Demand	0	0
Deposits, Money Market Deposits	0	0
Brokered cds and other time deposits fair value	0	0
Time Deposits	0	0
Deposits	0	0
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	0	0
Bank Term Funding Program Funding	0
Short-term Debt, Fair Value	0
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	0	0
Other long-term funding	0	0
Repayments of Lines of Credit	0	0
Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Commitments [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Interest Rate Lock Commitments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0	0
Foreign Currency Contract, Asset, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument | Interest Rate Contract
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument | Foreign Exchange Forward [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0	0
Foreign Currency Contract, Asset, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Interest Rate Contract
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 1 | US Treasury Securities | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	35,558	35,902
Held-to-maturity, Fair Value	969	963
Fair Value, Inputs, Level 1 | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 1 | Residential Related Securities | Fair Value, Measurements, Recurring | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 1 | Residential Related Securities | Fair Value, Measurements, Recurring | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 1 | Residential Related Securities | Fair Value, Measurements, Recurring | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 1 | Commercial mortgage-related securities | Fair Value, Measurements, Recurring | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 1 | Commercial mortgage-related securities | Fair Value, Measurements, Recurring | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 1 | Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Fair Value, Inputs, Level 1 | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Fair Value, Inputs, Level 1 | Other Debt Obligations | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Fair Value, Inputs, Level 1 | Available-for-sale Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	35,558	35,902
Fair Value, Inputs, Level 1 | Held-to-maturity Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity, Fair Value	969	963
Fair Value, Inputs, Level 2
Assets, Fair Value Disclosure [Abstract]
Bank and corporate owned life insurance	685,089	682,649
Liabilities, Fair Value Disclosure
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	1,333,411	1,940,194
Other long-term funding	536,055	541,269
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Cash and Due from Banks	0	0
Interest-bearing Deposits in Banks and Other Financial Institutions	0	0
Federal funds sold and securities purchased under agreements to resell	0	0
Equity Securities, FV-NI	0	0
FHLB and Federal Reserve Bank stocks	173,968	229,171
Residential Held-for-sale, Fair Value Disclosure	52,414	33,011
Loan, Held-for-Sale, Fair Value Disclosure		90,303
Loans Receivable, Fair Value Disclosure	0	0
Bank and corporate owned life insurance	685,089	682,649
Servicing Asset	0	0
Assets, Fair Value Disclosure	8,021,701	8,102,995
Liabilities, Fair Value Disclosure
Noninterest-bearing Domestic Deposit, Demand	0	0
Deposits, Savings Deposits	0	0
Interest-Bearing Domestic Deposit, Demand	0	0
Deposits, Money Market Deposits	0	0
Brokered cds and other time deposits fair value	3,931,230	4,447,479
Time Deposits	2,934,352	2,868,494
Deposits	6,865,582	7,315,973
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	265,661	326,757
Bank Term Funding Program Funding	497,959
Short-term Debt, Fair Value	763,620
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	1,320,280	1,944,600
Other long-term funding	517,009	534,983
Repayments of Lines of Credit	2,347	2,157
Liabilities, Fair Value Disclosure	9,707,013	10,326,755
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Foreign Exchange Forward [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	5,276	2,954
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	4,956	2,746
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Commitments [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Interest Rate Lock Commitments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	2,164	8,075
Foreign Currency Contract, Asset, Fair Value Disclosure	624	632
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument | Interest Rate Contract
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	10,685	930
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument | Foreign Exchange Forward [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	624	632
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	230	2,946
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	113,337	111,623
Foreign Currency Contract, Asset, Fair Value Disclosure	5,276	2,954
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Interest Rate Contract
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	222,303	195,662
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	4,956	2,746
Fair Value, Inputs, Level 2 | US Treasury Securities | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 2 | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	80,830	91,817
Held-to-maturity, Fair Value	1,523,658	1,553,984
Fair Value, Inputs, Level 2 | Residential Related Securities | Fair Value, Measurements, Recurring | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	1,090,998	1,120,794
Held-to-maturity, Fair Value	771,944	804,393
Fair Value, Inputs, Level 2 | Residential Related Securities | Fair Value, Measurements, Recurring | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	2,214,513	2,042,675
Held-to-maturity, Fair Value	44,457	46,170
Fair Value, Inputs, Level 2 | Residential Related Securities | Fair Value, Measurements, Recurring | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity, Fair Value	281,069	289,507
Fair Value, Inputs, Level 2 | Commercial mortgage-related securities | Fair Value, Measurements, Recurring | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	17,008	16,937
Held-to-maturity, Fair Value	628,928	632,914
Fair Value, Inputs, Level 2 | Commercial mortgage-related securities | Fair Value, Measurements, Recurring | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	152,232	154,793
Held-to-maturity, Fair Value	50,183	52,619
Fair Value, Inputs, Level 2 | Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	129,154	133,975
Fair Value, Inputs, Level 2 | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	890	1,051
Fair Value, Inputs, Level 2 | Other Debt Obligations | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	2,965	2,950
Fair Value, Inputs, Level 2 | Available-for-sale Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	3,688,590	3,564,990
Fair Value, Inputs, Level 2 | Held-to-maturity Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity, Fair Value	3,300,239	3,379,586
Fair Value, Inputs, Level 3
Assets, Fair Value Disclosure [Abstract]
Equity Securities, FV-NI	105	24,769	$ 19,225
Loans and Leases Receivable, Net Amount	29,138,257	28,865,124
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Cash and Due from Banks	0	0
Interest-bearing Deposits in Banks and Other Financial Institutions	0	0
Federal funds sold and securities purchased under agreements to resell	0	0
Equity Securities, FV-NI	105	24,769
FHLB and Federal Reserve Bank stocks	0	0
Residential Held-for-sale, Fair Value Disclosure	0	0
Loan, Held-for-Sale, Fair Value Disclosure		0
Loans Receivable, Fair Value Disclosure	27,739,448	27,371,086
Bank and corporate owned life insurance	0	0
Servicing Asset	85,226	84,390
Assets, Fair Value Disclosure	27,825,445	27,480,684
Liabilities, Fair Value Disclosure
Noninterest-bearing Domestic Deposit, Demand	6,254,135	6,119,956
Deposits, Savings Deposits	5,124,639	4,835,701
Interest-Bearing Domestic Deposit, Demand	8,747,127	8,843,967
Deposits, Money Market Deposits	6,721,674	6,330,453
Brokered cds and other time deposits fair value	0	0
Time Deposits	0	0
Deposits	26,847,575	26,130,076
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	0	0
Bank Term Funding Program Funding	0
Short-term Debt, Fair Value	0
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	0	0
Other long-term funding	0	0
Repayments of Lines of Credit	0	0
Liabilities, Fair Value Disclosure	26,847,797	26,130,749
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Commitments [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	222	673
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Interest Rate Lock Commitments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	666	439
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0	0
Foreign Currency Contract, Asset, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument | Interest Rate Contract
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Designated as Hedging Instrument | Foreign Exchange Forward [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0	0
Foreign Currency Contract, Asset, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Interest Rate Contract
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Liabilities, Fair Value Disclosure
Derivatives (trading liabilities)	0	0
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Not Designated as Hedging Instrument [Member] | Interest Rate Lock Commitments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	666	439
Fair Value, Inputs, Level 3 | US Treasury Securities | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 3 | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 3 | Residential Related Securities | Fair Value, Measurements, Recurring | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 3 | Residential Related Securities | Fair Value, Measurements, Recurring | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 3 | Residential Related Securities | Fair Value, Measurements, Recurring | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 3 | Commercial mortgage-related securities | Fair Value, Measurements, Recurring | US Government Sponsored-Enterprise Insured Loans
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 3 | Commercial mortgage-related securities | Fair Value, Measurements, Recurring | Government National Mortgage Association (GNMA) [Member]
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, Level 3 | Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Fair Value, Inputs, Level 3 | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Fair Value, Inputs, Level 3 | Other Debt Obligations | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Fair Value, Inputs, Level 3 | Available-for-sale Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
AFS investment securities, at fair value	0	0
Fair Value, Inputs, Level 3 | Held-to-maturity Securities [Member] | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity, Fair Value	0	0
Fair Value, Inputs, NAV | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure [Abstract]
Equity Securities, FV-NI	$ 12,500	$ 10,000