Segment Information - Assets Allocated by Segment (Detail) - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total Assets		$ 681,833	$ 972,246
Cash and cash equivalents		107,421	96,442	$ 98,761	$ 170,127
Income taxes receivable		3,228	12,056
Continuing Operations | Operating Segments | Real estate
Segment Reporting Information [Line Items]
Total Assets		504,552	691,238
Continuing Operations | Operating Segments | Mineral resources
Segment Reporting Information [Line Items]
Total Assets		39,182	39,469
Continuing Operations | Operating Segments | Other
Segment Reporting Information [Line Items]
Total Assets		18,483	19,106
Continuing Operations | Items not allocated to segments
Segment Reporting Information [Line Items]
Total Assets	[1]	117,771	117,466
Discontinued Operations
Segment Reporting Information [Line Items]
Total Assets	[1]	$ 1,845	$ 104,967

[1] Assets not allocated to segments at second quarter-end 2016 principally consist of cash and cash equivalents of $107,421,000 and an income tax receivable of $3,228,000. Assets not allocated to segments at year-end 2015 principally consist of cash and cash equivalents of $96,442,000 and an income tax receivable of $12,056,000.