Securities - Additional Information (Details)	3 Months Ended	12 Months Ended
Mar. 31, 2026 USD ($) Segment Security	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($) Security
Schedule Of Held To Maturity Securities [Line Items]
Number of Investment Securities Segments \| Segment	2
Credit losses	$ 0
Municipal securities percentage of securities portfolio	1.00%
Securities in Unrealized Loss Positions Qualitative Disclosure Number of Positions Greater Than or Equal to One Year \| Security	679		712
Gain (loss) on sale of investment securities	$ 0	$ 0
Available for Sale Securities, Amortized Cost Basis	356,090,000		$ 338,572,000
Debt Securities, Available-for-Sale	356,134,000		338,197,000
Collateralized Securities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Available for Sale Securities, Amortized Cost Basis	9,590,000,000		9,240,000,000
Debt Securities, Available-for-Sale	$ 8,810,000,000		$ 8,430,000,000
Securities Concentration Risk [Member] \| Stockholders' Equity, Total [Member] \| Other Than U.S. Government and Agencies [Member]
Schedule Of Held To Maturity Securities [Line Items]
Concentration Risk, Percentage	10.00%		10.00%

Debt securities, held-to-maturity credit loss.

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Municipal securities percentage of securities portfolio.

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The number of segments of investment securities held in a portfolio by an entity.

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Number of investment positions in investments that have been in a continuous unrealized loss position for greater than or equal to a year for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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