Concentration Risk (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) tenant	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) tenant	Sep. 30, 2018 USD ($)
Concentration Risk
Number of significant tenants | tenant	1		1
Rental income	$ 9,111	$ 11,216	$ 28,480	$ 31,214
Approximate total acres | Geographic concentration
Concentration Risk
Concentration risk (as a percent)			100.00%	100.00%
Approximate total acres | Geographic concentration | Cornbelt
Concentration Risk
Concentration risk (as a percent)			27.70%	28.20%
Approximate total acres | Geographic concentration | Delta and South
Concentration Risk
Concentration risk (as a percent)			17.60%	17.30%
Approximate total acres | Geographic concentration | High Plains
Concentration Risk
Concentration risk (as a percent)			19.80%	19.20%
Approximate total acres | Geographic concentration | Southeast
Concentration Risk
Concentration risk (as a percent)			27.60%	28.30%
Approximate total acres | Geographic concentration | West Coast
Concentration Risk
Concentration risk (as a percent)			7.30%	7.00%
Rental income | Tenant concentration | Tenant A
Concentration Risk
Rental income	$ 1,120	$ 2,193	$ 3,442	$ 4,409
Concentration risk (as a percent)	12.20%	19.50%	12.00%	14.10%
Rental income | Geographic concentration
Concentration Risk
Concentration risk (as a percent)	100.00%	100.00%	100.00%	100.00%
Rental income | Geographic concentration | Cornbelt
Concentration Risk
Concentration risk (as a percent)	35.30%	33.50%	35.10%	35.70%
Rental income | Geographic concentration | Delta and South
Concentration Risk
Concentration risk (as a percent)	11.80%	8.30%	11.50%	9.60%
Rental income | Geographic concentration | High Plains
Concentration Risk
Concentration risk (as a percent)	6.20%	7.60%	8.20%	8.20%
Rental income | Geographic concentration | Southeast
Concentration Risk
Concentration risk (as a percent)	26.30%	21.50%	25.60%	23.40%
Rental income | Geographic concentration | West Coast
Concentration Risk
Concentration risk (as a percent)	20.40%	29.00%	19.60%	23.10%