Disclosures about Fair Value of Assets and Liabilities - Fair Value Measurements of Assets and Liabilities Recognized on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 1,015,343	$ 834,776
U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	6,239	1,413
State and municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	678,459	405,768
Federal agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	185,849	269,252
Federal agency mortgage-backed pools
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	132,472	146,572
Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	12,324	11,771
Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,015,343	834,776
Recurring Basis | U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	6,239	1,413
Recurring Basis | State and municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	678,459	405,768
Recurring Basis | Federal agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	185,849	269,252
Recurring Basis | Federal agency mortgage-backed pools
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	132,472	146,572
Recurring Basis | Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	12,324	11,771
Recurring Basis | Interest rate swap agreements asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	40,434	11,422
Recurring Basis | Forward sale commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	1,584	264
Recurring Basis | Interest rate swap agreements liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	(49,331)	(15,861)
Recurring Basis | Commitments to originate loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value		(38)
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Federal agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Federal agency mortgage-backed pools
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swap agreements asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Forward sale commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swap agreements liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	0	0
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commitments to originate loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value		0
Recurring Basis | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,015,343	834,776
Recurring Basis | Significant Other Observable Inputs (Level 2) | U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	6,239	1,413
Recurring Basis | Significant Other Observable Inputs (Level 2) | State and municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	678,459	405,768
Recurring Basis | Significant Other Observable Inputs (Level 2) | Federal agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	185,849	269,252
Recurring Basis | Significant Other Observable Inputs (Level 2) | Federal agency mortgage-backed pools
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	132,472	146,572
Recurring Basis | Significant Other Observable Inputs (Level 2) | Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	12,324	11,771
Recurring Basis | Significant Other Observable Inputs (Level 2) | Interest rate swap agreements asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	40,434	11,422
Recurring Basis | Significant Other Observable Inputs (Level 2) | Forward sale commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	1,584	264
Recurring Basis | Significant Other Observable Inputs (Level 2) | Interest rate swap agreements liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	(49,331)	(15,861)
Recurring Basis | Significant Other Observable Inputs (Level 2) | Commitments to originate loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value		(38)
Recurring Basis | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | State and municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | Federal agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | Federal agency mortgage-backed pools
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | Interest rate swap agreements asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | Forward sale commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | Interest rate swap agreements liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value	$ 0	0
Recurring Basis | Significant Unobservable Inputs (Level 3) | Commitments to originate loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, fair value		$ 0