Loans and Allowance for Loan Losses - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 43,309,877,000		$ 43,404,490,000
Land held for future development, period	1 year
Financing receivable, allowance for credit loss	$ 492,661,000	$ 457,010,000	479,385,000	$ 443,424,000
Reserve for unfunded commitments	53,600,000		57,200,000
All financing receivable, allowance for credit loss	546,200,000		$ 536,600,000
Increase (decrease) in allowance for credit loss	$ 9,600,000
ACL to loans ratio (as percent)	1.26%		1.24%
Allowance for credit loss, reasonable and supportable forecast period (in year)	2 years
Allowance for credit loss, straight-line basis historical period (in year)	1 year
Allowance for credit loss, measurement input, estimated peak weighted average unemployment rate	4.40%		4.50%
Financing receivable, modified, subsequent default	$ 71,600,000
Commitments to land additional funds to TDRs	0		$ 0
Total consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-off of previously established reserves for credit losses associated with the transfer to held for sale		6,600,000	31,300,000
Reclassification to held-for-sale		424,100,000
Financing receivable, allowance for credit loss	$ 126,552,000	$ 137,930,000	126,657,000	$ 138,299,000
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan substandard period (in days)	90 days
Loss
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan charge off (in days)	120 days
Asset Pledged as Collateral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 24,790,000,000		$ 24,310,000,000