Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Securities available for sale	$ 1,005,426	$ 1,135,317
Estimate of Fair Value Measurement [Member]
Assets
State tax credits held for sale	48,327	39,046
Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	10,200	10,046
Obligations of states and political subdivisions
Assets
Securities available for sale	366,122	213,024
Agency mortgage-backed securities
Assets
Securities available for sale	605,949	902,021
US Treasury Bill Securities [Member]
Assets
Securities available for sale	11,521	10,226
Corporate Debt Securities [Member]
Assets
Securities available for sale	11,634
Recurring basis \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	1,005,426	1,135,317
Derivatives	33,999	11,055
Total assets	1,039,425	1,146,372
Liabilities
Derivatives	44,240	14,747
Total liabilities	44,240	14,747
Recurring basis \| Obligations of U.S. Government-sponsored enterprises \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	10,200	10,046
Recurring basis \| Obligations of states and political subdivisions \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	366,122	213,024
Recurring basis \| Agency mortgage-backed securities \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	605,949	902,021
Recurring basis \| US Treasury Bill Securities [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	11,521	10,226
Recurring basis \| Corporate Debt Securities [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	11,634
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Derivatives	0	0
Total assets	0	0
Liabilities
Derivatives	0	0
Total liabilities	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Obligations of states and political subdivisions
Assets
Securities available for sale	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Agency mortgage-backed securities
Assets
Securities available for sale	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| US Treasury Bill Securities [Member]
Assets
Securities available for sale	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Corporate Debt Securities [Member]
Assets
Securities available for sale	0
Recurring basis \| Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	1,005,426	1,135,317
Derivatives	33,999	11,055
Total assets	1,039,425	1,146,372
Liabilities
Derivatives	44,240	14,747
Total liabilities	44,240	14,747
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	10,200	10,046
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Obligations of states and political subdivisions
Assets
Securities available for sale	366,122	213,024
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Agency mortgage-backed securities
Assets
Securities available for sale	605,949	902,021
Recurring basis \| Significant Other Observable Inputs (Level 2) \| US Treasury Bill Securities [Member]
Assets
Securities available for sale	11,521	10,226
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Corporate Debt Securities [Member]
Assets
Securities available for sale	11,634
Recurring basis \| Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Derivatives	0	0
Total assets	0	0
Liabilities
Derivatives	0	0
Total liabilities	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Obligations of states and political subdivisions
Assets
Securities available for sale	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Agency mortgage-backed securities
Assets
Securities available for sale	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| US Treasury Bill Securities [Member]
Assets
Securities available for sale	0	$ 0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Corporate Debt Securities [Member]
Assets
Securities available for sale	$ 0

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value of financial and nonfinancial obligations.

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