Commitments and Contingent Liabilities - Summary of Contract or Notional Amount of Outstanding Loan and Lease Commitments (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Commitments And Contingencies Liabilities [Line Items]
Fixed Rate	$ 51,885	$ 76,081
Variable Rate	970,502	963,062
Total	1,022,387	1,039,143
Commitments to Extend Credit
Commitments And Contingencies Liabilities [Line Items]
Fixed Rate	51,101	74,099
Variable Rate	930,778	928,991
Total	981,879	1,003,090
Letters of Credit
Commitments And Contingencies Liabilities [Line Items]
Fixed Rate	784	1,982
Variable Rate	39,724	34,071
Total	$ 40,508	$ 36,053