Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Securities available for sale	$ 641,382	$ 460,797
State tax credits held for sale	400
Portion at Other than Fair Value, Fair Value Disclosure
Assets
State tax credits held for sale	43,100
Total Fair Value
Assets
Securities available for sale	641,382	460,797
State tax credits held for sale	44,271	41,264
Derivative financial instruments	3,589	4,016
Liabilities
Derivative financial instruments	3,589	4,016
Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	99,224	107,660
Obligations of states and political subdivisions
Assets
Securities available for sale	34,642	36,631
Residential mortgage-backed securities
Assets
Securities available for sale	507,516	316,506
Recurring basis \| Total Fair Value
Assets
Securities available for sale	641,382	460,797
State tax credits held for sale	400	3,585
Derivative financial instruments	3,589	4,016
Assets, Fair Value Disclosure	645,371	468,398
Liabilities
Derivative financial instruments	3,589	4,016
Total liabilities	3,589	4,016
Recurring basis \| Obligations of U.S. Government-sponsored enterprises \| Total Fair Value
Assets
Securities available for sale	99,224	107,660
Recurring basis \| Obligations of states and political subdivisions \| Total Fair Value
Assets
Securities available for sale	34,642	36,631
Recurring basis \| Residential mortgage-backed securities \| Total Fair Value
Assets
Securities available for sale	507,516	316,506
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	0
Derivative financial instruments	0	0
Assets, Fair Value Disclosure	0	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	641,382	457,708
State tax credits held for sale	0	0
Derivative financial instruments	3,589	4,016
Assets, Fair Value Disclosure	644,971	461,724
Liabilities
Derivative financial instruments	3,589	4,016
Total liabilities	3,589	4,016
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	99,224	107,660
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Obligations of states and political subdivisions
Assets
Securities available for sale	34,642	33,542
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Residential mortgage-backed securities
Assets
Securities available for sale	507,516	316,506
Recurring basis \| Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	3,089
State tax credits held for sale	400	3,585
Derivative financial instruments	0	0
Assets, Fair Value Disclosure	400	6,674
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	3,089
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Residential mortgage-backed securities
Assets
Securities available for sale	$ 0	$ 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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