Taxes - Constituents of Deferred Tax Assets (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Non-current deferred tax assets:
Stock-based compensation expense	$ 15,365,000	$ 13,895,000
Federal and state tax credit carryforwards	5,154,000	5,091,000
Inventory and revenue related	2,919,000	2,985,000
Depreciation	2,882,000	2,328,000
Bonuses, commissions, and other compensation	2,483,000	2,500,000
Other	3,714,000	4,175,000
Gross non-current deferred tax assets	32,517,000	30,974,000
Non-current deferred tax liabilities:
Nondeductible intangible assets	(379,000)	(1,198,000)
Gross non-current deferred tax liabilities	(379,000)	(1,198,000)
Valuation allowance	(4,116,000)	(3,259,000)
Net non-current deferred tax assets	28,022,000	26,517,000
Non-current deferred tax liabilities:
Other	0	(319,000)
Net non-current deferred tax liabilities	$ 0	$ (319,000)