Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Securities available for sale	$ 721,369	$ 641,382
Total Fair Value
Assets
Securities available for sale	721,369	641,382
State tax credits held for sale	39,169	44,271
Derivative financial instruments	3,023	3,589
Liabilities
Derivative financial instruments	3,023	3,589
Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	98,498	99,224
Obligations of states and political subdivisions
Assets
Securities available for sale	26,810	34,642
Residential mortgage-backed securities
Assets
Securities available for sale	586,136	507,516
Recurring basis \| Total Fair Value
Assets
Securities available for sale	721,369	641,382
State tax credits held for sale		400
Other Investments	121
Derivative financial instruments	3,023	3,589
Assets, Fair Value Disclosure	724,513	645,371
Liabilities
Derivative financial instruments	3,023	3,589
Total liabilities	3,023	3,589
Recurring basis \| Obligations of U.S. Government-sponsored enterprises \| Total Fair Value
Assets
Securities available for sale	98,498	99,224
Recurring basis \| Obligations of states and political subdivisions \| Total Fair Value
Assets
Securities available for sale	26,810	34,642
Recurring basis \| Residential mortgage-backed securities \| Total Fair Value
Assets
Securities available for sale	586,136	507,516
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
State tax credits held for sale		0
Other Investments	121
Derivative financial instruments	0	0
Assets, Fair Value Disclosure	121	0
Liabilities
Derivative financial instruments	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) \| Residential mortgage-backed securities
Assets
Securities available for sale	0	0
Recurring basis \| Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	721,369	641,382
State tax credits held for sale		0
Other Investments	0
Derivative financial instruments	3,023	3,589
Assets, Fair Value Disclosure	724,392	644,971
Liabilities
Derivative financial instruments	3,023	3,589
Total liabilities	3,023	3,589
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	98,498	99,224
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Obligations of states and political subdivisions
Assets
Securities available for sale	26,810	34,642
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Residential mortgage-backed securities
Assets
Securities available for sale	586,136	507,516
Recurring basis \| Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
State tax credits held for sale		400
Other Investments	0
Derivative financial instruments	0	0
Assets, Fair Value Disclosure	0	400
Liabilities
Derivative financial instruments	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) \| Residential mortgage-backed securities
Assets
Securities available for sale	$ 0	$ 0

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