Income Taxes - Deferred Tax Reconciliation (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Net of Valuation Allowance [Abstract]
Accrued warranty	$ 657	$ 919
Inventory	3,631	2,697
Net operating loss carryforwards	57,294	59,784
Tax credit carryforwards	22,075	22,817
Stock-based compensation	1,995	2,142
Fixed assets	1,808	952
Goodwill	1,603	2,109
Deferred revenue	2,906	2,950
Subsidiary service accruals	1,702	0
Other	2,082	2,748
Total deferred tax assets	95,753	97,118
Less: valuation allowance	(88,566)	(86,752)
Net deferred tax assets	7,187	10,366
Deferred tax liabilities:
Intangible assets	(5,603)	(7,582)
Other	(467)	(1,611)
Total deferred tax liabilities	(6,070)	(9,193)
Total net deferred tax assets	$ 1,117	$ 1,173