Securities (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2026 USD ($) security	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($) security	Jun. 30, 2025 USD ($)	Dec. 31, 2025 USD ($) security
Debt and Equity Securities, FV-NI [Line Items]
Provision for credit losses	$ 0	$ 900,000	$ 0	$ 700,000
Allowance for credit losses for AFS securities	$ 0		$ 0		$ 0
Number of securities in an unrealized loss position | security	887		887		718
Total fair value	$ 18,781,600,000		$ 18,781,600,000		$ 11,672,900,000
Debt securities, unrealized losses	$ 128,900,000		$ 128,900,000		$ 158,700,000
Percentage of debt securities, held-to-maturity, portfolio	1		1		1
Proceeds from sale of debt securities	$ 1,100,000,000	0	$ 1,100,000,000	0
Loss on sale of debt securities	$ (73,900,000)	$ 0	$ (73,900,000)	$ 0
Rating of A or higher
Debt and Equity Securities, FV-NI [Line Items]
Percentage of debt securities, held-to-maturity, portfolio	0.94		0.94		0.96