Fair Value Measurements (Narrative) (Details) shares in Millions, $ in Millions	Mar. 31, 2025 USD ($) security	Dec. 31, 2024 USD ($) security	Jun. 30, 2016 shares	Jun. 30, 2015 shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate market value	$ 30,464.3	$ 29,001.5
Visa Class B
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shares issued (in shares) | shares			1.1	1.0
LEVEL 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of available for sale securities portfolio | security	945	940
Aggregate market value	$ 22,500.0	$ 21,600.0
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		0.200
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		0.200