Combined Guarantor Subsidiaries - Mortgage and Other Notes Receivable - Summary (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Mortgage and Other Notes Receivable [Line Items]
Mortgage and other notes receivable	[1]	$ 7,406	$ 7,672
Mortgages
Mortgage and Other Notes Receivable [Line Items]
Mortgage and other notes receivable		4,807	4,884
Other Notes Receivable
Mortgage and Other Notes Receivable [Line Items]
Mortgage and other notes receivable		2,599	2,788
Guarantor Subsidiaries
Mortgage and Other Notes Receivable [Line Items]
Mortgage and other notes receivable		76,729	76,747
Guarantor Subsidiaries | Mortgages
Mortgage and Other Notes Receivable [Line Items]
Mortgage and other notes receivable		$ 75,499	$ 75,517
Guarantor Subsidiaries | Mortgages | The Promenade
Mortgage and Other Notes Receivable [Line Items]
Interest rate (as a percent)		5.00%	5.00%
Mortgage and other notes receivable		$ 47,514	$ 47,514
Guarantor Subsidiaries | Mortgages | Hamilton Corner
Mortgage and Other Notes Receivable [Line Items]
Interest rate (as a percent)		5.67%	5.67%
Mortgage and other notes receivable		$ 14,295	$ 14,295
Guarantor Subsidiaries | Mortgages | Forum at Grandview
Mortgage and Other Notes Receivable [Line Items]
Interest rate (as a percent)		5.25%	5.25%
Mortgage and other notes receivable		$ 12,400	$ 12,400
Guarantor Subsidiaries | Mortgages | Village Square
Mortgage and Other Notes Receivable [Line Items]
Interest rate (as a percent)		4.00%	4.00%
Mortgage and other notes receivable		$ 1,290	$ 1,308
Guarantor Subsidiaries | Other Notes Receivable
Mortgage and Other Notes Receivable [Line Items]
Mortgage and other notes receivable		$ 1,230	$ 1,230
Guarantor Subsidiaries | Other Notes Receivable | Community improvement district
Mortgage and Other Notes Receivable [Line Items]
Interest rate (as a percent)		7.50%	7.50%
Mortgage and other notes receivable		$ 1,230	$ 1,230

[1] As of March 31, 2019, includes $609,856 of assets related to consolidated variable interest entities that can be used only to settle obligations of the consolidated variable interest entities and $406,466 of liabilities of consolidated variable interest entities for which creditors do not have recourse to the general credit of the Company. See Note 7.