Income Taxes - Expense (benefit) reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Taxes
Statutory federal income tax rate (as a percent)			21.00%	21.00%
Tax at the federal statutory rate	$ 1,854	$ 420	$ 5,278	$ 7,402
State income taxes (net of federal benefit)	311	88	885	1,532
Change in state tax rate	1,187		1,187
2017 qualified timber gains at the federal statutory rate of 23.8%				(524)
Decrease in valuation allowance		(3,480)		(4,931)
Change in federal AMT credit carryforward		(511)		(511)
Other	(349)		(252)	(153)
Total income tax expense (benefit)	$ 3,003	$ (3,483)	$ 7,098	$ 2,815
Timber statutory federal rate				23.80%