Investment Securities - Narrative (Details) - USD ($)	3 Months Ended				9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2022	Sep. 30, 2021	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Debt securities, reclassified	$ 3,600,000,000
Proceeds from sale of available-for-sale securities	3,200,000,000
Pre-tax loss	$ 625,600,000
Estimated tax rate	21.946%
Debt securities, available-for-sale, transfer to held-to-maturity			$ 1,990,000,000	$ 500,800,000
Available-for-sale, transfer to held-to-maturity, gain (loss)					$ 0
Debt securities, held-to-maturity transfer, unrealized loss					99,400,000
Held to maturity mortgage backed securities							$ 3,639,850,000
Available for sale mortgage backed securities	$ 3,723,974,000				3,723,974,000		2,852,774,000
Available-for-sale, interest receivable	23,300,000				23,300,000
Available-for-sale securities	3,319,277,000				3,319,277,000		2,529,426,000
Securities valued at less than historical cost, amount	$ 2,691,716,000				$ 2,691,716,000		2,467,223,000
Securities valued at less than historical cost (as percent)	81.10%				81.10%
Provision for credit losses, AFS securities	$ 0	$ 0			$ 0	$ 0
Provision for credit loss expense (recapture)	(3,214,000)	0			(3,214,000)	0
Securities pledged as collateral	2,050,000,000.00				2,050,000,000.00		2,360,000,000
Realized gains	0	0			0	0
Realized losses	801,500,000	28,400,000			$ 801,500,000	$ 28,400,000
Income tax benefit related to security gains (losses) (as percent)					26.135%	26.135%
Variable rate commercial MBS
Debt Securities, Available-for-sale [Line Items]
Held to maturity mortgage backed securities							136,000,000.0
Available for sale mortgage backed securities	608,700,000				$ 608,700,000		517,200,000
Residential Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Held to maturity mortgage backed securities							934,100,000
Available for sale mortgage backed securities	$ 1,640,000,000				$ 1,640,000,000		$ 875,500,000
Bonds
Debt Securities, Available-for-sale [Line Items]
Investments sold, amount		$ 251,500,000				$ 251,500,000