Senior Notes, Secured, and Unsecured Indebtedness - Schedule of Maturities of Construction Notes Payable (Footnote) (Details)	9 Months Ended
	Sep. 30, 2017
Construction Notes Payable, March 2014, August 2015, November 2015, March 2016 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.00%
Construction Notes Payable, March 2014, August 2015, November 2015, March 2016 | Prime rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Construction Notes Payable, January 2016 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.25%
Construction Notes Payable, November 2014, April 2015, July 2015 | Prime rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Construction Notes Payable Five [Member] | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Construction Notes Payable Five [Member] | Federal Funds Effective Swap Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%