Loans Receivable - Nonaccrual Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	$ 13,703	$ 10,703
Commercial business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	12,564	9,098
Commercial business | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	6,639	3,110
Commercial business | Owner-occupied commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	4,212	4,090
Commercial business | Non-owner occupied commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	1,713	1,898
One-to-four family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	71	81
Real estate construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	899	1,247
Real estate construction and land development | One-to-four family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	899	1,247
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross nonaccrual loans	$ 169	$ 277