Related Party and Affiliated Real Estate Joint Venture Transactions - (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Related Party Transaction Due From To Related Party [Line Items]
Management fees as a percentage of cash collected from total revenues	6.00%
Number of three-year revolving lines of credit to joint ventures	1
SPI [Member]
Related Party Transaction Due From To Related Party [Line Items]
Basis points multiplied by the total asset value for asset management fee	0.50%
SpenAero, L.C. [Member]
Related Party Transaction Due From To Related Party [Line Items]
Cash paid for related party transactions	$ 1,180	$ 1,163	$ 1,059