Income Taxes - Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of income taxes computed using the federal statutory rate to the taxes reported in consolidated statements of operations
Loss before income taxes	$ 16,340	$ 19,920	$ 15,622
Federal statutory rate	34.00%	34.00%	34.00%
Taxes computed at federal statutory rate	$ (5,556)	$ (6,773)	$ (5,311)
State taxes (net of federal benefit)	(392)	(463)	0
Warrants	(118)	(10)	(1,815)
Nondeductible stock compensation	543	48	81
Michigan NOL benefit	0	0	(791)
Net operating loss expirations	0	655	612
Write-off of Section 382 limited NOL’s	0	67,781	0
Write-off of Section 383 limited R&D credits	0	1,600	0
Other	57	352	(27)
Tax Adjustments, Settlements, and Unusual Provisions	(5,203)	0	0
Change in valuation allowance	10,669	(63,190)	7,251
Reported income taxes	0	0	$ 0
Deferred tax assets
Net operating loss carryforwards	13,998	7,092
Employee benefits and stock compensation	2,485	1,897
Research and development costs	4,903	2,184
Fixed assets	453	254
Intangible assets	(477)	(510)
Asset retirement obligation	0	127
Inventory reserve	510	186
Other, net	143	115
Total deferred tax assets	22,015	11,345
Valuation allowance	(22,015)	(11,345)
Net deferred tax assets	$ 0	$ 0