Fair Value Measurements - Recurring Basis (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Assets:
Investment securities available-for-sale:	$ 1,339,408,000	$ 1,243,693,000
Equity securities	39,708,000	41,452,000
Other liabilities
Liabilities:
Liability derivatives	54,897,000	85,193,000
Other liabilities \| Interest rate swaps \| Derivatives designated as hedging instruments:
Liabilities:
Liability derivatives	157,000	228,000
U.S. government and agencies
Assets:
Investment securities available-for-sale:	20,614,000	20,984,000
Government-sponsored entities
Assets:
Investment securities available-for-sale:	141,485,000	147,786,000
Municipal bonds
Assets:
Investment securities available-for-sale:	342,395,000	346,588,000
Mortgage-backed securities
Assets:
Investment securities available-for-sale:	834,914,000	728,335,000
Fair Value, Measurements, Recurring
Assets:
Investment securities available-for-sale:	1,339,408,000	1,243,693,000
Equity securities	39,708,000
Trading securities held in the “rabbi trust”	7,633,000	7,204,000
Liabilities:
Deferred compensation “rabbi trust”	7,633,000	7,204,000
Fair Value, Measurements, Recurring \| U.S. government and agencies
Assets:
Investment securities available-for-sale:	20,614,000	20,984,000
Fair Value, Measurements, Recurring \| Government-sponsored entities
Assets:
Investment securities available-for-sale:	141,485,000	147,786,000
Fair Value, Measurements, Recurring \| Municipal bonds
Assets:
Investment securities available-for-sale:	342,395,000	346,588,000
Fair Value, Measurements, Recurring \| Mortgage-backed securities
Assets:
Investment securities available-for-sale:	834,914,000	728,335,000
Fair Value, Measurements, Recurring \| Derivatives - interest rate customer swaps
Assets:
Derivatives	53,682,000	83,255,000
Liabilities:
Derivatives	54,529,000	84,590,000
Fair Value, Measurements, Recurring \| Interest rate swaps
Liabilities:
Derivatives	157,000	228,000
Fair Value, Measurements, Recurring \| Risk participation agreements
Assets:
Derivatives	28,000	49,000
Liabilities:
Derivatives	211,000	375,000
Fair Value, Measurements, Recurring \| Quoted prices in active markets for identical assets (Level 1)
Assets:
Investment securities available-for-sale:	0	0
Equity securities	39,708,000	41,452,000
Trading securities held in the “rabbi trust”	7,633,000	7,204,000
Liabilities:
Deferred compensation “rabbi trust”	7,633,000	7,204,000
Fair Value, Measurements, Recurring \| Quoted prices in active markets for identical assets (Level 1) \| U.S. government and agencies
Assets:
Investment securities available-for-sale:	0	0
Fair Value, Measurements, Recurring \| Quoted prices in active markets for identical assets (Level 1) \| Government-sponsored entities
Assets:
Investment securities available-for-sale:	0	0
Fair Value, Measurements, Recurring \| Quoted prices in active markets for identical assets (Level 1) \| Municipal bonds
Assets:
Investment securities available-for-sale:	0	0
Fair Value, Measurements, Recurring \| Quoted prices in active markets for identical assets (Level 1) \| Mortgage-backed securities
Assets:
Investment securities available-for-sale:	0	0
Fair Value, Measurements, Recurring \| Quoted prices in active markets for identical assets (Level 1) \| Derivatives - interest rate customer swaps
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Fair Value, Measurements, Recurring \| Quoted prices in active markets for identical assets (Level 1) \| Interest rate swaps
Liabilities:
Derivatives	0	0
Fair Value, Measurements, Recurring \| Quoted prices in active markets for identical assets (Level 1) \| Risk participation agreements
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2)
Assets:
Investment securities available-for-sale:	1,339,408,000	1,243,693,000
Equity securities	0	0
Trading securities held in the “rabbi trust”	0	0
Liabilities:
Deferred compensation “rabbi trust”	0	0
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| U.S. government and agencies
Assets:
Investment securities available-for-sale:	20,614,000	20,984,000
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| Government-sponsored entities
Assets:
Investment securities available-for-sale:	141,485,000	147,786,000
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| Municipal bonds
Assets:
Investment securities available-for-sale:	342,395,000	346,588,000
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| Mortgage-backed securities
Assets:
Investment securities available-for-sale:	834,914,000	728,335,000
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| Derivatives - interest rate customer swaps
Assets:
Derivatives	53,682,000	83,255,000
Liabilities:
Derivatives	54,529,000	84,590,000
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| Interest rate swaps
Liabilities:
Derivatives	157,000	228,000
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| Risk participation agreements
Assets:
Derivatives	28,000	49,000
Liabilities:
Derivatives	211,000	375,000
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3)
Assets:
Investment securities available-for-sale:	0	0
Equity securities	0	0
Trading securities held in the “rabbi trust”	0	0
Liabilities:
Deferred compensation “rabbi trust”	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| U.S. government and agencies
Assets:
Investment securities available-for-sale:	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| Government-sponsored entities
Assets:
Investment securities available-for-sale:	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| Municipal bonds
Assets:
Investment securities available-for-sale:	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| Mortgage-backed securities
Assets:
Investment securities available-for-sale:	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| Derivatives - interest rate customer swaps
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| Interest rate swaps
Liabilities:
Derivatives	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| Risk participation agreements
Assets:
Derivatives	0	0
Liabilities:
Derivatives	$ 0	$ 0

Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value of financial and nonfinancial obligations.

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