Summary of Unsecured Lines of Credit (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Line Of Credit Facility [Line Items]
Lines of credit		$ 40,000,000
Bankers Trust Operating [Member]
Line Of Credit Facility [Line Items]
Lines of credit	$ 0
3.31% Interest Bearing Line of Credit [Member] | Bankers Trust [Member]
Line Of Credit Facility [Line Items]
Line of credit facility maximum borrowing capacity	40,000,000
Unsecured Lines of Credit [Member]
Line Of Credit Facility [Line Items]
Lines of credit		40,000,000
Line of credit facility maximum borrowing capacity	47,500,000	47,500,000
Unsecured Lines of Credit [Member] | 3.31% Interest Bearing Line of Credit [Member] | Bankers Trust [Member]
Line Of Credit Facility [Line Items]
Line of credit facility maximum borrowing capacity	$ 40,000,000
Debt instrument, maturity date	May 31, 2018
Variable / Fixed	Variable
Reset Frequency	Monthly
Line of credit facility, interest rate during period	3.31%
Unsecured Lines of Credit [Member] | 4.06% Interest Bearing Line of Credit [Member] | Bankers Trust Operating [Member]
Line Of Credit Facility [Line Items]
Line of credit facility maximum borrowing capacity	$ 7,500,000
Debt instrument, maturity date	May 31, 2018
Variable / Fixed	Variable
Reset Frequency	Monthly
Line of credit facility, interest rate during period	4.06%
Unsecured Lines of Credit [Member] | 3.13% Interest Bearing Line of Credit [Member] | Bankers Trust [Member]
Line Of Credit Facility [Line Items]
Lines of credit		40,000,000
Line of credit facility maximum borrowing capacity		$ 40,000,000
Debt instrument, maturity date		May 31, 2018
Variable / Fixed		Variable
Reset Frequency		Monthly
Line of credit facility, interest rate during period		3.13%
Unsecured Lines of Credit [Member] | 3.88% Interest Bearing Line of Credit [Member] | Bankers Trust Operating [Member]
Line Of Credit Facility [Line Items]
Line of credit facility maximum borrowing capacity		$ 7,500,000
Debt instrument, maturity date		Mar. 31, 2018
Variable / Fixed		Variable
Reset Frequency		Monthly
Line of credit facility, interest rate during period		3.88%