Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2007
Debt Instrument [Line Items]
Total debt	$ 69,726	$ 63,804
In-substance defeased debt, interest payable at 5.62%, secured and paid by pledged cash and treasury securities, due October 1, 2015
Debt Instrument [Line Items]
Total debt	25,324	25,670	$ 29,300
Community Development District debt, secured by certain real estate and standby note purchase agreements, due through May 2039, interest payable at 2.25% to 7.0% | Community Development District debt, secured by certain real estate and standby note purchase agreements, due through May 2039, interest payable at 2.25% to 7.0%
Debt Instrument [Line Items]
Total debt	6,777	6,516
Construction loan in the Pier Park North joint venture, due February 2016, bearing interest at LIBOR plus 210 basis points, or 2.30% and 2.26% at September 30, 2015 and December 31, 2014, respectively | Pier Park North Joint Venture Construction Loan
Debt Instrument [Line Items]
Total debt	$ 37,625	$ 31,618