Disclosures About Fair Value of Assets and Liabilities - Fair Value Measurements of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	$ 1,824,160	$ 1,790,025
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap asset	0	0
Interest rate swap liability	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	1,821,673	1,787,132
Significant Other Observable Inputs (Level 2) | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap asset	82,010	27,855
Interest rate swap liability	84,254	29,299
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,487	2,893
Significant Unobservable Inputs (Level 3) | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap asset	0	0
Interest rate swap liability	0	0
U.S. Treasury
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	300
U.S. Treasury | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0
U.S. Treasury | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	300
U.S. Treasury | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0
U.S. Treasury | Fair Value, Measurements, Recurring | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	300
U.S. Government-sponsored agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,444	38,875
U.S. Government-sponsored agency securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
U.S. Government-sponsored agency securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,444	38,875
U.S. Government-sponsored agency securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
U.S. Government-sponsored agency securities | Fair Value, Measurements, Recurring | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,444	38,875
State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	1,146,946	899,796
State and municipal | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
State and municipal | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	1,144,494	896,938
State and municipal | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,452	2,858
State and municipal | Fair Value, Measurements, Recurring | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	1,146,946	899,796
U.S. Government-sponsored mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	670,395	851,323
U.S. Government-sponsored mortgage-backed securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
U.S. Government-sponsored mortgage-backed securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	670,391	851,319
U.S. Government-sponsored mortgage-backed securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	4	4
U.S. Government-sponsored mortgage-backed securities | Fair Value, Measurements, Recurring | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	670,395	851,323
Corporate obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	4,075	31
Corporate obligations | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Corporate obligations | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	4,044	0
Corporate obligations | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	31	31
Corporate obligations | Fair Value, Measurements, Recurring | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	4,075	31
Interest rate swap asset | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap asset	0	0
Interest rate swap liability	0	0
Interest rate swap asset | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap asset	82,010	27,855
Interest rate swap liability	84,254	29,299
Interest rate swap asset | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap asset	0	0
Interest rate swap liability	0	0
Interest rate swap asset | Fair Value, Measurements, Recurring | Fair Value | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap asset	82,010	27,855
Interest rate swap liability	$ 84,254	$ 29,299