Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
State net operating loss carryforwards	$ 14,316	$ 15,709
Impairment losses	36,751	38,907
Prepaid income from land sales	3,180	2,597
Capitalized costs	2,468	2,107
Reserves and accruals	1,672	1,789
Unrealized losses on investments	2,282	1,008
Other	765	711
Total gross deferred tax assets	61,434	62,828
Deferred tax liabilities:
Investment in real estate and property and equipment basis differences	4,000	2,358
Deferred gain on land sales and involuntary conversions	24,956	19,236
Installment sales	83,275	83,268
Pension Plan assets transferred to the 401(k) Plan	580	872
Other	1,431	1,409
Total gross deferred tax liabilities	114,242	107,143
Net deferred tax liabilities	$ (52,808)	$ (44,315)