Real Estate Joint Ventures - Consolidated Real Estate Joint Ventures (Details) - item			9 Months Ended	12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2018	Dec. 31, 2017	Apr. 30, 2017
Pier Park Crossings JV
Variable interest entity
Number of units					240
Variable interest entity, ownership percentage			75.00%	75.00%
Windmark
Variable interest entity
Variable interest entity, ownership percentage			49.00%	49.00%
Pier Park North
Variable interest entity
Variable interest entity, ownership percentage			60.00%	60.00%
Artisan Park, L.L.C
Variable interest entity
Variable interest entity, ownership percentage	100.00%	74.00%