Senior Notes, Secured, and Unsecured Indebtedness - Schedule of Maturities of Construction Notes Payable (Footnote) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Gain on extinguishment of debt	$ 383	$ 0
Construction Notes Payable, January 2016 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.25%
May 2018, Maturity May 2021 Construction Notes Payable | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
May 2018, Maturity May 2021 Construction Notes Payable | Federal Funds Effective Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
May 2018, Maturity June 2020 Construction Notes Payable | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	2.90%