Accounting for the Impairment of Long-Lived Assets and Fee Development Contracts (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Line Items]
Impairment charges - real estate assets	$ 9,650,000	$ 0	$ 9,650,000	$ 0
Loss on fee development contracts	0	0	0	0
Expensed pursuit costs	4,772,000	$ 772,000	4,957,000	$ 882,000
Houston [Member]
Property, Plant and Equipment [Line Items]
Impairment charges - real estate assets	$ 9,700,000		$ 9,700,000