Unused Available Lines of Credit (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Unsecured Debt [Member]
Line of Credit Facility [Line Items]
Line of credit amount	$ 68,000
Unsecured Debt [Member] | US Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	20,000
Unsecured Debt [Member] | Wells Fargo Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	15,000
Unsecured Debt [Member] | PNC Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	12,000
Unsecured Debt [Member] | Frost National Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	10,000
Unsecured Debt [Member] | JPM Chase Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	6,000
Unsecured Debt [Member] | UMB Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	5,000
Secured Debt [Member] | UMB Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	50,000
Secured Debt [Member] | Federal Home Loan Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	204,789
Secured Debt [Member] | First Tennessee Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	$ 50,000