Income Taxes - Schedule of Significant Components of the Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 19,006	$ 15,399
Research and development credits	3,858	2,806
Other state credits	1,923	989
Inventory	2,203	2,560
Allowances and bad debts	840	596
Accrued warranty	5,732	3,387
Accrued wages and benefits	413	351
Other accrued expenses	5,281	2,906
Stock-based compensation	649	645
Capitalized research and development costs	770	1,090
Intangible amortization	2,240	1,734
Contract liabilities (deferred revenue)	495	339
Other	2,490	152
Total deferred tax assets	45,900	32,954
Valuation allowance	(44,405)	(31,992)	$ (17,800)
Total deferred tax assets, net of valuation allowance	1,495	962
Deferred tax liabilities:
Tax depreciation in excess of book depreciation on property, plant and equipment	(2,142)	(1,665)
Total deferred tax liabilities	(2,142)	(1,665)
Net deferred tax liability	$ (647)	$ (703)