Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets
Securities available for sale	$ 1,099,185	$ 721,369
State tax credits held for sale	0	0
Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	1,099,185	721,369
State tax credits held for sale	39,355	39,169
Derivative financial instruments	6,703	3,023
Liabilities
Derivative financial instruments	7,967	3,023
Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	53,781	98,498
Obligations of states and political subdivisions
Assets
Securities available for sale	116,985	26,810
Residential mortgage-backed securities
Assets
Securities available for sale	897,544	586,136
US Treasury Bill Securities [Member]
Assets
Securities available for sale	10,077	9,925
Corporate Debt Securities [Member]
Assets
Securities available for sale	20,798
Recurring basis \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	1,099,185	721,369
Other investments	145	121
Derivative financial instruments	6,703	3,023
Total assets	1,106,033	724,513
Liabilities
Derivative financial instruments		3,023
Total liabilities	7,967	3,023
Recurring basis \| Obligations of U.S. Government-sponsored enterprises \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	53,781	98,498
Recurring basis \| Obligations of states and political subdivisions \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	116,985	26,810
Recurring basis \| Residential mortgage-backed securities \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	897,544	586,136
Recurring basis \| US Treasury Bill Securities [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	10,077	9,925
Recurring basis \| Corporate Debt Securities [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Securities available for sale	20,798
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Other investments	145	121
Derivative financial instruments	0	0
Total assets	145	121
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 \| 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	1,099,185	721,369
Other investments	0	0
Derivative financial instruments	6,703	3,023
Total assets	1,105,888	724,392
Liabilities
Derivative financial instruments	7,967	3,023
Total liabilities	7,967	3,023
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Obligations of U.S. Government-sponsored enterprises
Assets
Securities available for sale	53,781	98,498
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Obligations of states and political subdivisions
Assets
Securities available for sale	116,985	26,810
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Residential mortgage-backed securities
Assets
Securities available for sale	897,544	586,136
Recurring basis \| Significant Other Observable Inputs (Level 2) \| US Treasury Bill Securities [Member]
Assets
Securities available for sale	10,077	9,925
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Corporate Debt Securities [Member]
Assets
Securities available for sale	20,798
Recurring basis \| Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Other investments	0	0
Derivative financial instruments	0	0
Total assets	0	0
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
Recurring basis \| Significant Unobservable Inputs (Level 3) \| US Treasury Bill Securities [Member]
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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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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