Fair Value Measurements (Narrative) (Details) $ in Millions	Mar. 31, 2026 USD ($) security	Dec. 31, 2025 USD ($) security
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for Sale	$ 36,913.2	$ 34,036.5
LEVEL 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of level 2 available for sale securities in portfolio | security	1,057	1,003
Available for Sale	$ 28,900.0	$ 25,900.0
LEVEL 3 | Fair Value, Measurements, Nonrecurring | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans fair value	$ 1.3	$ 1.3
LEVEL 3 | Fair Value, Measurements, Nonrecurring | Measurement Input, Discount Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.25	0.400
LEVEL 3 | Fair Value, Measurements, Nonrecurring | Measurement Input, Discount Rate | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans fair value	$ 1.3	$ 1.3
LEVEL 3 | Fair Value, Measurements, Nonrecurring | Measurement Input, Discount Rate | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.250	0.400