Income Taxes - Components of Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets:
Accrued expenses	$ 393	$ 561
Deferred revenues	209	654
Capitalization of costs	2,138	3,224
Pension adjustment	2,996	4,690
Stock grant expense	2,130	2,309
State deferred taxes	0	37
Book deferred gains	941	1,912
Joint venture allocations	1,025	932
Provision for additional capitalized costs	699	1,003
Interest rate swap	267	799
Other	423	41
Total deferred income tax assets	11,221	16,162
Deferred income tax liabilities:
Deferred gains	32	51
Depreciation	3,563	5,279
Cost of sales allocations	872	1,252
Joint venture allocations	3,972	5,389
Straight line rent	631	926
Prepaid expenses	132	323
State deferred taxes	322	470
Other	135	190
Total deferred income tax liabilities	9,659	13,880
Net deferred income tax asset	1,562	2,282
Allowance for deferred tax assets	0	0
Net deferred taxes	$ 1,562	$ 2,282