Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Other operating	$ 1,895	$ 1,935
Parking Income
Disaggregation of Revenue [Line Items]
Other operating	1,626	1,568
Rental Lease Guaranty
Disaggregation of Revenue [Line Items]
Other operating	175	224
Management Fee Income
Disaggregation of Revenue [Line Items]
Other operating	68	99
Miscellaneous
Disaggregation of Revenue [Line Items]
Other operating	$ 26	$ 44