Fair Value Measurements - Narrative (Detail) shares in Millions, $ in Millions	Dec. 31, 2025 USD ($) security shares	Dec. 31, 2024 USD ($) security	Jun. 30, 2016 shares	Jun. 30, 2015 shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	$ 34,036.5	$ 29,001.5
Common stock issued (in shares) | shares	245.2
LEVEL 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of available for sale securities in portfolio | security	1,003	940
Available for sale	$ 25,900.0	$ 21,600.0
LEVEL 3 | Visa Class B
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock issued (in shares) | shares			1.1	1.0
Fair Value, Measurements, Nonrecurring | LEVEL 3 | Measurement Input, Discount Rate | Valuation, Market Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.400	0.200
Fair value	$ 1.3	$ 19.1
Fair Value, Measurements, Nonrecurring | LEVEL 3 | Measurement Input, Discount Rate | Weighted Average | Valuation, Market Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.400	0.200