Derivatives (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Derivative [Line Items]
Notional amount of derivatives	$ 7,474,521,000		$ 7,474,521,000		$ 7,392,532,000
Fair value hedges resulting net earnings	(1,520,000)	$ (10,592,000)	(6,037,000)	$ (22,559,000)
Fair value liability	1,600,000		1,600,000		2,100,000
Credit risk-related contingent features, net liability position	21,900,000		21,900,000		39,100,000
Credit risk-related contingent features, posted collateral	22,300,000		22,300,000		38,000,000
Fair Value Hedging [Member]
Derivative [Line Items]
Fair value hedges resulting net earnings	40,000,000		203,500,000
Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Notional amount of derivatives	2,102,500,000		2,102,500,000		1,827,500,000
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 3, Expires 2025 [Member]
Derivative [Line Items]
Notional amount of derivatives	50,000,000		$ 50,000,000
Derivative maturity expiration year			2025
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 4, Expires 2026 [Member]
Derivative [Line Items]
Notional amount of derivatives	425,000,000		$ 425,000,000
Derivative maturity expiration year			2026
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 5, Expires 2027 [Member]
Derivative [Line Items]
Notional amount of derivatives	825,000,000		$ 825,000,000
Derivative maturity expiration year			2027
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 6, Expires 2028 [Member]
Derivative [Line Items]
Notional amount of derivatives	50,000,000		$ 50,000,000
Derivative maturity expiration year			2028
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 7, Expires 2029 [Member]
Derivative [Line Items]
Notional amount of derivatives	275,000,000		$ 275,000,000
Derivative maturity expiration year			2029
Interest Rate Swaps - Securities [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Notional amount of derivatives	477,500,000		$ 477,500,000		$ 477,500,000
Fair value hedges resulting net earnings	4,690,000	$ 3,114,000	8,600,000	$ 6,222,000
Derivative hedged item	450,800,000		450,800,000
Basis adjustment associated with hedged items loss	26,700,000		26,700,000
Interest Rate Swaps - Securities [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedging [Member] | Commercial Mortgage-Backed Securities [Member]
Derivative [Line Items]
Amortized cost basis of closed portfolio of pre-payable securities	$ 514,000,000		$ 514,000,000