Derivative Financial Instruments (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Derivative Financial Instruments
Notional Amount	$ 24,934,490,000		$ 24,452,059,000
Estimated Fair Value Gain	$ 176,784,000		$ 172,939,000
Derivative, Gain, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Estimated Fair Value Loss	$ 954,788,000		$ 804,486,000
Derivative, Loss, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Fair value of the interest rate swap derivatives, other assets	$ 174,000,000.0		$ 169,000,000.0
Reduction in derivative asset fair value	781,100,000		635,300,000
Fair value of the interest rate swap derivatives, other liabilities	954,300,000,000		803,500,000,000
Estimated gain (loss) on fair value	381,000,000		2,600,000
Obligation under forward commitments, the fair value of those obligations along with the fair value of derivative instruments associated with forward commitments
Fair value of forward commitments	(954,788,000)		(804,486,000)
Mortgage loan pipeline
Obligation under forward commitments, the fair value of those obligations along with the fair value of derivative instruments associated with forward commitments
Obligation	117,590,000		65,051,000
Expected closures
Obligation under forward commitments, the fair value of those obligations along with the fair value of derivative instruments associated with forward commitments
Obligation	102,911,000		54,993,000
Cash flow hedge | Borrower
Derivative Financial Instruments
Collateral provided	237,800,000
Cash flow hedge | Interest-bearing deposits | Counterparty
Derivative Financial Instruments
Cash collateral	53,700,000
Interest rate contracts
Derivative Financial Instruments
Notional Amount	22,900,000,000		22,600,000,000
Mortgage servicing rights hedging | Non-designated hedges
Derivative Financial Instruments
Notional Amount	107,000,000.0		142,000,000.0
Mortgage servicing rights hedging | Non-designated hedges | Other Assets
Derivative Financial Instruments
Notional Amount	107,000,000		142,000,000
Estimated Fair Value Gain	$ 381,000		$ 2,605,000
Derivative, Gain, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Derivative, Loss, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Mortgage loan pipeline commitments hedging
Obligation under forward commitments, the fair value of those obligations along with the fair value of derivative instruments associated with forward commitments
Obligation	$ 2,030,000		$ 1,154,000
Mortgage loan pipeline commitments hedging | Non-designated hedges | Other Assets and Other Liabilities
Derivative Financial Instruments
Notional Amount	123,000,000		77,500,000
Estimated Fair Value Gain	$ 2,030,000		$ 1,154,000
Derivative, Gain, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Estimated Fair Value Loss	$ 491,000		$ 947,000
Derivative, Loss, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Forward commitments
Obligation under forward commitments, the fair value of those obligations along with the fair value of derivative instruments associated with forward commitments
Obligation	$ 123,000,000		$ 77,500,000
Fair value of forward commitments	(491,000)		(947,000)
Customer swaps | Cash flow hedge
Derivative Financial Instruments
Collateral provided	99,500,000
Foreign exchange swaps
Derivative Financial Instruments
Gain or loss recorded	0	$ 0
Interest rate swap
Derivative Financial Instruments
Gain or loss recorded	113,000	$ 96,000
Interest rate swap | Fair Value Hedging | Counterparty
Derivative Financial Instruments
Notional Amount	9,100,000		9,200,000
Amortized cost basis of loans hedged	9,600,000		9,700,000
Interest rate swap | Fair Value Hedging | Other Assets | Counterparty
Derivative Financial Instruments
Notional Amount	9,099,000		9,188,000
Estimated Fair Value Gain	$ 373,000		$ 220,000
Derivative, Gain, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Derivative, Loss, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Interest rate swap | Non-designated hedges | Other Assets and Other Liabilities | Borrower
Derivative Financial Instruments
Notional Amount	$ 11,513,291,000		$ 11,327,419,000
Estimated Fair Value Gain	$ 29,960,000		$ 60,145,000
Derivative, Gain, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Estimated Fair Value Loss	$ 954,297,000		$ 803,539,000
Derivative, Loss, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Interest rate swap | Non-designated hedges | Other Assets | Counterparty
Derivative Financial Instruments
Notional Amount	$ 11,422,100,000		$ 11,235,952,000
Estimated Fair Value Gain	$ 144,041,000		$ 108,820,000
Derivative, Gain, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Derivative, Loss, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Reduction in derivative asset fair value	$ 781,100,000
Interest rate swap | Economic hedges | Counterparty
Derivative Financial Instruments
Notional Amount	1,800,000,000
Estimated Fair Value Loss	1,000,000		$ 5,000,000
Interest rate swap | Economic hedges | Other Assets | Counterparty
Derivative Financial Instruments
Notional Amount	$ 1,760,000,000		$ 1,660,000,000
Derivative, Gain, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other
Estimated Fair Value Loss	$ 1,000		$ 5,000
Derivative, Loss, Statement of Income or Comprehensive Income [Extensible Enumeration]	Noninterest Income, Other		Noninterest Income, Other