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	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	$ 1,003,799	$ 999,947
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	999,833	995,969
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	3,966	3,978
Fair Value, Measurements, Recurring | Interest rate swap liability | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap liability	12,065	8,688
Fair Value, Measurements, Recurring | U.S. Government-sponsored agency securities | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	6,498
Fair Value, Measurements, Recurring | State and municipal | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	506,303	522,750
Fair Value, Measurements, Recurring | State and municipal | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	3,931	3,943
Fair Value, Measurements, Recurring | U.S. Government-sponsored mortgage-backed securities | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	487,032	470,866
Fair Value, Measurements, Recurring | U.S. Government-sponsored mortgage-backed securities | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	4
Fair Value, Measurements, Recurring | Corporate obligations | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	31	31
Fair Value, Measurements, Recurring | Equity securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities
Fair Value, Measurements, Recurring | Equity securities | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		2,353
Fair Value, Measurements, Recurring | Equity securities | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		4
Fair Value, Measurements, Recurring | Interest rate swap asset | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate derivatives	11,376	7,305
Fair Value, Measurements, Recurring | Interest rate cap | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate derivatives	258	18
Fair Value, Measurements, Recurring | Fair Value | Interest rate swap liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap liability	12,065	8,688
Fair Value, Measurements, Recurring | Fair Value | U.S. Government-sponsored agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	6,498
Fair Value, Measurements, Recurring | Fair Value | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	510,234	526,693
Fair Value, Measurements, Recurring | Fair Value | U.S. Government-sponsored mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	487,036	470,866
Fair Value, Measurements, Recurring | Fair Value | Corporate obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	31	31
Fair Value, Measurements, Recurring | Fair Value | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities		2,357
Fair Value, Measurements, Recurring | Fair Value | Interest rate swap asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate derivatives	11,376	7,305
Fair Value, Measurements, Recurring | Fair Value | Interest rate cap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate derivatives	$ 258	$ 18