Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities transferred to Held-to-Maturity	$ 0	$ 1,059,737,000	$ 0	$ 873,600,000	$ 179,800,000
Unrealized after tax gain (loss) on available-for-sale securities transferred to the held-to-maturity portfolio		(1,500,000)		$ 69,000,000	$ (2,200,000)
Allowance for credit losses - securities held-to-maturity	(1,707,000)	(1,608,000)
Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement	209,500,000
Proceeds from Sale of Debt Securities, Available-for-sale	312,574,000	29,501,000	37,457,000
Debt Securities, Available-for-sale, Realized Gain	321,000	292,000	769,000
Debt Securities, Available-for-sale, Realized Loss	20,000,000	136,000	$ 10,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	258,224,000	325,426,000
Debt Securities, Available-for-sale, Unrealized Loss Position	3,265,473,000	$ 3,007,832,000
Securities pledged as collateral
Debt Securities, Available-for-sale [Line Items]
Financial Instruments, Owned, at Fair Value	2,100,000,000
Securities pledged as collateral
Debt Securities, Available-for-sale [Line Items]
Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement	$ 209,500,000