Business Segment Data - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2016 Segment Commercial_Loan MortgageLoan	Mar. 31, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Number of operating segment | Segment	4
Number of commercial loan investments	4
Golf operation description	Our golf operations consist of a single property located in the City, with two 18-hole championship golf courses
Income Property Operations [Member] | Identifiable Assets [Member]
Segment Reporting Information [Line Items]
Concentration risk percentage	68.20%		68.60%
Income Property Operations [Member] | Consolidated Revenues [Member]
Segment Reporting Information [Line Items]
Concentration risk percentage	35.00%	58.30%
Commercial Mortgage Loan [Member]
Segment Reporting Information [Line Items]
Number of fixed-rate commercial mortgage loan investment	1
Mezzanine Loan [Member]
Segment Reporting Information [Line Items]
Number of fixed-rate commercial mortgage loan investment | MortgageLoan	1