Income Taxes - Significant Components of Deferred Taxes (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Real estate	$ 37,513	$ 50,759
Employee benefits	1,510	13,185
Net operating loss carryforwards	2,305	2,804
Oil and gas properties	0	1,672
AMT credits	1,690	5,900
Income producing properties	794	2,055
Oil and gas percentage depletion carryforwards	0	3,478
Accruals not deductible until paid	196	552
Gross deferred tax assets	44,008	80,405
Valuation allowance	(39,578)	(73,405)
Deferred tax asset net of valuation allowance	4,430	7,000
Deferred Tax Liabilities:
Undeveloped land	0	(1,359)
Convertible debt	(2,402)	(5,035)
Timber	0	(283)
Gross deferred tax liabilities	2,402	6,677
Deferred tax asset, net	$ 2,028	$ 323