Senior Notes, Secured, and Unsecured Indebtedness - Schedule of Maturities of Construction Notes Payable (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total notes payable	$ 185,817	$ 175,181
Construction Loans
Debt Instrument [Line Items]
Total notes payable	275,600
Outstanding	136,800
Construction Loans | March 2016 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	33,400
Outstanding	$ 14,700
Current Rate	3.44%
Construction Loans | January 2016 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 35,000
Outstanding	$ 17,600
Current Rate	3.68%
Construction Loans | November 2015 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 42,500
Outstanding	$ 15,300
Current Rate	4.50%
Construction Loans | August 2015 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 14,200
Outstanding	$ 2,800
Current Rate	4.50%
Construction Loans | August 2015 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 37,500
Outstanding	$ 10,400
Current Rate	4.50%
Construction Loans | July 2015 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 22,500
Outstanding	$ 14,900
Current Rate	4.00%
Construction Loans | April 2015 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 18,500
Outstanding	$ 13,200
Current Rate	4.00%
Construction Loans | November 2014 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 24,000
Outstanding	$ 17,200
Current Rate	4.00%
Construction Loans | November 2014 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 22,000
Outstanding	$ 15,500
Current Rate	4.00%
Construction Loans | March 2014 Construction Notes Payable
Debt Instrument [Line Items]
Total notes payable	$ 26,000
Outstanding	$ 15,200
Current Rate	3.43%