Income Taxes - Components of Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets:
Accrued liabilities	$ 614	$ 519
Allowance for doubtful accounts	95	51
Derivative Contracts	110	0
Disallowed Interest Carryforwards	0	769
Alternative minimum tax credits	1,720	4,760
State Net operating loss carry-forwards	821	469
Percentage depletion carry-forwards	0	0
General Business Credits	0	137
Total deferred tax assets	3,360	6,705
Deferred Tax Liabilities:
Basis differences relating to managed partnerships	2,109	2,296
Depletion and depreciation	37,173	36,711
Derivative Contracts	0	526
Total deferred tax liabilities	39,282	39,533
Net deferred tax liabilities	$ 35,922	$ 32,828