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Investment Securities - Additional Information (Details)
 12 Months Ended
Dec. 31, 2021
USD ($)
security
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Summary of Investment Holdings [Line Items]      
Securities pledged to secure public and other funds, carrying value $ 2,701,000,000 $ 2,427,000,000  
Allowance for credit losses for available-for-sale debt securities 0 0  
Accrued interest receivable on available-for-sale debt securities $ 35,500,000 27,000,000  
Number of securities in security portfolio | security 1,918    
Number of securities in unrealized loss position | security 357    
Equity securities, at fair value $ 13,211,000 2,547,000  
Gains on equity securities 200,000 1,400,000 $ 700,000
Impairments on equity securities without readily determinable fair value 0 117,000 0
Downward adjustments on equity securities without readily determinable fair value 0 117,000 $ 0
Other Assets      
Summary of Investment Holdings [Line Items]      
Equity securities without readily determinable fair value 186,000,000 $ 105,800,000  
Indiana      
Summary of Investment Holdings [Line Items]      
Investment securities issued by states and political subdivisions, market value $ 647,600,000    
State and political subdivision investment, equity percentage 21.50%    
Percentage of municipal bonds rated A or better 97.00%    
Percentage of non rated local interest bonds 3.00%