Income Tax Expense (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred:
Net operating loss carryforwards	$ 101,423	$ 124,881
Accrued expenses	5,617	6,582
Tax credits	11,826	11,314
Bad debt	78	91
Inventory	2,160	4,424
Capitalized research and development	16,079	21,374
Deferred compensation	2,535	3,596
Other	1,099	964
Deferred tax asset	140,817	173,226
Valuation allowance	(118,551)	(133,784)
Total deferred tax assets	22,266	39,442
Deferred Tax Liabilities, Net [Abstract]
Depreciation and amortization	(8,961)	(15,316)
Convertible debt	(3,740)	(9,760)
Other	0	0
Total deferred tax liabilities	(22,467)	(40,321)
Net deferred tax liability	(201)	(879)
Trademarks and trade names
Deferred Tax Liabilities, Net [Abstract]
Intangible assets	(733)	(1,027)
Developed Technology and Trademark
Deferred Tax Liabilities, Net [Abstract]
Intangible assets	$ (9,033)	$ (14,218)