Contingent Liabilities and Commitments with Off-Balance Sheet Risk - Summary of Financial Instruments with Off-Balance-Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Contract or Notional Amount
Commitments to extend credit	$ 982,739	$ 807,651
Unfunded limited partner equity commitment	7,252	10,914
Secured
Contract or Notional Amount
Standby letters of credit and financial guarantees written	17,736	12,913
Unsecured
Contract or Notional Amount
Standby letters of credit and financial guarantees written	$ 847	$ 681