Segment Information - Assets Allocated by Segment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013		Jun. 30, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total Assets	$ 1,222,352		$ 1,172,152
Cash and cash equivalents	184,168		192,307		69,138	10,361
Deferred tax asset, net	34,519		40,398
Operating Segments [Member] | Real estate [Member]
Segment Reporting Information [Line Items]
Total Assets	612,076		582,802
Operating Segments [Member] | Oil And Gas [Member]
Segment Reporting Information [Line Items]
Total Assets	343,164		312,553
Operating Segments [Member] | Other natural resources [Member]
Segment Reporting Information [Line Items]
Total Assets	26,103		23,478
Items not allocated to segments [Member] | Assets not allocated to segments [Member]
Segment Reporting Information [Line Items]
Total Assets	$ 241,009	[1]	$ 253,319	[1]

[1] Assets not allocated to segments at second quarter-end 2014 principally consist of cash and cash equivalents of $184,168,000 and a net deferred tax asset of $34,519,000. Assets not allocated to segments at year-end 2013 principally consist of cash and cash equivalents of $192,307,000 and a net deferred tax asset of $40,398,000.