Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Net long-term deferred assets and (liabilities) relating to:
Accounts receivable and inventory reserves	$ 625	$ 1,052
Warranty accrual	3,675	3,776
Other accruals	1,406	1,044
Share-based compensation	7,568	4,102
Intangibles	993	(33)
Oklahoma investment credit carryforward	3,404	0
Other, net	3,119	2,608
Gross deferred income tax assets	20,790	12,549
Valuation allowance	(3,404)	0
Net deferred income tax assets	17,386	12,549
Property & equipment	(49,379)	(40,873)
Total deferred income tax liabilities	(49,379)	(40,873)
Net deferred income tax liabilities	$ 31,993	$ 28,324