Temporary Differences in Financial Statement Carrying Amounts and Tax Bases of Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax asset
Inventories	$ 1,416	$ 2,912
State income taxes		328
Program accrual	7,306	7,529
Vacation pay accrual	815	756
Accrued bonuses	589	599
Bad debt expense	952	627
Stock compensation	2,079	2,755
NOL carryforward	2,142	1,141
Tax credits	931	824
Lease liability	3,378	3,308
Accrued expenses	347	334
Other	967	(125)
Deferred tax asset	20,922	20,988
Deferred tax liability
Plant and equipment, principally due to differences in depreciation and capitalized interest	36,878	35,545
Lease asset	3,332	3,265
Prepaid expenses	1,508	1,323
Deferred tax liability	41,718	40,133
Total net deferred tax liability	$ 20,796	$ 19,145

Deferred tax assets lease liability.

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Deferred tax assets liabilities state taxes.

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Deferred Tax Assets Other Current.

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Deferred tax liabilities lease asset.

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from inventory.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from employee bonuses.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from employee compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from reserves and accruals.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from accrued liabilities.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from the allowance for doubtful accounts.

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Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting.

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Amount of deferred tax consequences attributable to taxable temporary differences derived from prepaid expenses.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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