Segment Information - Segment Revenues and Earnings (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues		$ 30,866	$ 33,136	$ 28,015	$ 22,305	$ 64,497	$ 47,207	$ 47,992	$ 37,618	$ 114,322	$ 197,314	$ 218,576
Depreciation, depletion and amortization										5,463	11,447	45,085
Equity in earnings of unconsolidated ventures		7,026	$ 1,764	$ 2,747	$ 6,362	2,251	$ 3,637	$ 188	$ 47	17,899	6,123	16,008
Income (loss) before taxes from continuing operations										50,043	90,815	8,214
Total assets		761,912				733,208				761,912	733,208
Investment in unconsolidated ventures		64,579				77,611				64,579	77,611	82,453
Capital expenditures										2,452	6,138	14,690
Assets of discontinued operations		0				14				0	14	104,967
Real Estate
Segment Reporting Information [Line Items]
Revenues										20,923
Operating Segments | Real Estate
Segment Reporting Information [Line Items]
Revenues										112,746	190,273	202,830
Depreciation, depletion and amortization										131	976	7,605
Equity in earnings of unconsolidated ventures										16,500	5,778	15,582
Income (loss) before taxes from continuing operations										47,281	121,420	67,678
Investment in unconsolidated ventures		64,579				77,611				64,579	77,611	82,453
Capital expenditures										52	5,783	13,644
Operating Segments | Oil and Gas
Segment Reporting Information [Line Items]
Revenues										1,502	5,076	9,094
Depreciation, depletion and amortization										28	145	383
Equity in earnings of unconsolidated ventures										1,395	173	275
Income (loss) before taxes from continuing operations										45,552	3,327	4,230
Investment in unconsolidated ventures		0				0				0	0	0
Capital expenditures										2,400	0	59
Operating Segments | Other Natural Resources
Segment Reporting Information [Line Items]
Revenues										74	1,965	6,652
Depreciation, depletion and amortization										25	352	540
Equity in earnings of unconsolidated ventures										4	172	151
Income (loss) before taxes from continuing operations										(6,393)	(4,625)	(608)
Investment in unconsolidated ventures		0				0				0	0	0
Capital expenditures										0	299	745
Items Not Allocated To Segments
Segment Reporting Information [Line Items]
Revenues										0	0	0
Depreciation, depletion and amortization										5,279	7,772	8,166
Equity in earnings of unconsolidated ventures										0	0	0
Income (loss) before taxes from continuing operations	[1]									(36,397)	(29,307)	(63,086)
Investment in unconsolidated ventures		0				0				0	0	0
Capital expenditures										0	56	242
Continuing Operations
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization										5,463	9,245	$ 16,694
Total assets	[2]	761,912				733,194				761,912	733,194
Continuing Operations | Operating Segments | Real Estate
Segment Reporting Information [Line Items]
Total assets	[2]	386,222				403,062				386,222	403,062
Continuing Operations | Operating Segments | Oil and Gas
Segment Reporting Information [Line Items]
Total assets	[2]	0				38,907				0	38,907
Continuing Operations | Operating Segments | Other Natural Resources
Segment Reporting Information [Line Items]
Total assets	[2]	3,346				11,531				3,346	11,531
Continuing Operations | Items Not Allocated To Segments
Segment Reporting Information [Line Items]
Total assets	[2]	$ 372,344				$ 279,694				$ 372,344	$ 279,694

[1] Items not allocated to segments consist of: For the Year 2017 2016 2015 (In thousands)General and administrative expense$(50,354) $(18,274) $(24,802)Share-based and long-term incentive compensation expense(7,201) (4,425) (4,474)Gain on sale of assets28,674 48,891 —Interest expense(8,532) (19,985) (34,066)Loss on extinguishment of debt, net(611) (35,864) —Other corporate non-operating income1,627 350 256 $(36,397) $(29,307) $(63,086)

[2] Total assets excludes assets of discontinued operations of $14,000 and $104,967,000 in 2016 and 2015.