Derivatives (Fair Values of Derivative Financial Instruments) (Details) - USD ($)		3 Months Ended	12 Months Ended
		Mar. 31, 2024	Dec. 31, 2023
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		$ 7,680,572,000	$ 7,691,719,000
Fair Values, Assets		$ 94,614,000	$ 84,458,000
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other Assets	Other Assets
Fair Values, Assets	[1]	$ 174,564,000	$ 156,360,000
Less: netting adjustment	[1]	(79,875,000)	(65,648,000)	[2]
Total derivative assets/liabilities	[1]	94,689,000	90,712,000
Fair Values, Liabilities		97,599,000	87,567,000
Fair Values, Liabilities	[1]	235,380,000	207,138,000
Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Total derivative assets/liabilities	[1]	235,380,000	207,138,000
Derivatives Designated as Hedging Instruments [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		2,027,500,000	2,027,500,000
Fair Values, Assets	[1]	31,347,000	22,819,000
Fair Values, Liabilities	[1]	90,143,000	73,611,000
Derivatives Not Designated as Hedging Instruments [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		5,653,072,000	5,664,219,000
Fair Values, Assets	[1]	143,217,000	133,541,000
Fair Values, Liabilities	[1]	145,237,000	133,527,000
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		5,094,695,000	5,128,144,000
Fair Values, Assets	[1]	141,396,000	131,271,000
Fair Values, Liabilities	[1]	141,539,000	129,994,000
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		348,091,000	364,906,000
Fair Values, Assets	[1]	9,000	34,000
Fair Values, Liabilities	[1]	4,000	18,000
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		39,373,000	13,355,000
Fair Values, Assets	[1]	842,000
Fair Values, Liabilities	[1]	1,000	286,000
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		24,981,000	18,563,000
Fair Values, Assets	[1]		372,000
Fair Values, Liabilities	[1]	569,000	0
Derivatives Not Designated as Hedging Instruments [Member] | To Be Announced (TBA) Securities [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		20,250,000	13,500,000
Fair Values, Assets	[1]	9,000
Fair Values, Liabilities	[1]	46,000	47,000
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		83,065,000	83,134,000
Fair Values, Assets	[1]	961,000	1,864,000
Fair Values, Liabilities	[1]	937,000	1,840,000
Derivatives Not Designated as Hedging Instruments [Member] | Visa Class B derivative contract [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		42,617,000	42,617,000
Fair Values, Liabilities	[1]	2,141,000	1,342,000
Cash Flow Hedge [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Variable Rate Loans [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		1,550,000,000	1,550,000,000
Fair Values, Liabilities	[1]	$ 90,143,000	$ 73,611,000
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Variable Rate Loans [Member]
Derivatives Fair Value [Line Items]
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other Assets	Other Assets
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other Liabilities	Other Liabilities
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Securities [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		$ 477,500,000	$ 477,500,000
Fair Values, Assets	[1]	$ 31,347,000	$ 22,819,000
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other Assets	Other Assets
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other Liabilities	Other Liabilities

[1] Derivative assets and liabilities are reported in other assets or other liabilities, respectively, in the consolidated balance sheets.

[2] Represents balance sheet netting of derivative assets and liabilities for variation margin collateral held or placed with the same central clearing counterparty. See offsetting assets and liabilities for further information.