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Income Taxes - Summary of Unrecognized Tax Benefits and Temporary Differences (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Unrecognized tax benefits |  |
Balance at the beginning of the period | $ 330 | $ 270
Decreases related to current year tax positions | 0 | 66
Decreases due to tax positions expired | (317) | (6)
Balance at the end of the period | 13 | 330
Uncertain tax positions, reserved for tax exposure in Europe | 0 | 300
Uncertain tax positions, reserved for tax exposure in Europe, released during the year | 300 |
Deferred tax assets: |  |
Unearned lease revenue | 2,217 | 2,519
State taxes | 0 | 10
Inventory | 1,486 | 2,153
Reserves and allowances | 6,781 | 4,356
Other accruals | 2,577 | 1,769
Foreign tax credit | 0 | 0
Lease liability | 146 | 198
Net operating loss carry forward | 68,168 | 74,045
California alternative minimum tax credit | 33 | 33
Charitable contributions | 2 | 65
Total deferred tax assets | 81,410 | 85,148
Less: valuation allowance | (518) | (468)
Net deferred tax assets | 80,892 | 84,680
Deferred tax liabilities: |  |
Depreciation and impairment on aircraft engines and equipment | (183,131) | (163,773)
Inventory | 0 | 0
Notes receivable | (15,911) | (34,426)
Right of use liability | (139) | (184)
Other deferred tax liabilities | (4,595) | (4,616)
Net deferred tax liabilities | (203,776) | (202,999)
Other comprehensive (income) loss deferred tax liability | (1,448) |
Other comprehensive (income) loss deferred tax liability |  | 1,481
Net deferred tax liabilities | (124,332) | $ (116,838)
Federal |  |
Deferred tax liabilities: |  |
Operating loss carryforwards | 316,300 |
State |  |
Deferred tax liabilities: |  |
Operating loss carryforwards | 2,200 |
State | California Franchise Tax Board |  |
Deferred tax liabilities: |  |
Valuation allowance of net operating loss | 500 |
State | Georgia Department of Revenue |  |
Deferred tax liabilities: |  |
Valuation allowance of net operating loss | $ 100 |

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