Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income (loss)	$ 8,587	$ (80,856)	$ (47,386)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Stock-based compensation	9,492	8,006	6,157
Stock-based compensation, restructuring	0	201	0
Depreciation	1,625	1,806	1,599
Amortization of debt issuance costs and non-cash interest	457	569	2,017
Change in fair value of warrant liabilities	(25,332)	21,927	(11,811)
Change in fair value of embedded derivatives	14	(759)	147
Loss on disposal and impairment of property and equipment	838	0	9
Loss on debt extinguishment	1,254	0	0
Net gain on sale of business	(79,980)	0	0
Changes in operating assets and liabilities:
Trade accounts receivable	(2,212)	(1,022)	(730)
Inventory	(3,503)	2,950	3,890
Prepaid expenses and other current assets	(9,200)	(2,004)	163
Other assets	(4,367)	(1,747)	11
Accounts payable and accrued expenses	5,645	6,142	2,194
Restructuring liabilities	0	4	0
Deferred revenue	15,658	(137)	(8,462)
Deferred rent	208	0	0
Net cash used in operating activities	(80,816)	(44,920)	(52,202)
Investing activities:
Purchases of property and equipment	(122)	(810)	(293)
Proceeds from sale of business	89,624	0	0
Restricted cash from sale of business	(8,500)	0	0
Acquisition of business, net of cash acquired	(20,000)	0	0
Net cash provided by (used in) investing activities	61,002	(810)	(293)
Financing activities:
Proceeds from borrowings of debt and revolving credit facility, net of issuance costs	27,977	0	9,900
Payments on borrowings of debt	(40,041)	0	(25,000)
Payments on revolving credit facility	0	0	(15,051)
Proceeds from exercise of common stock options and warrants	1,506	833	33
Proceeds from issuance of common stock and common stock warrants, net of issuance costs	556	75,690	67,316
Net cash provided (used) by financing activities	(10,002)	76,523	37,198
Net (decrease) increase in cash and cash equivalents	(29,816)	30,793	(15,297)
Cash and cash equivalents at beginning of period	72,021	41,228	56,525
Cash and cash equivalents at end of period	42,205	72,021	41,228
Supplemental disclosure of cash flow information:
Cash paid for interest	12,847	2,463	5,284
Noncash investing and financing activities:
Issuance of common stock in conjunction with acquisition	15,237	0	0
Purchase of property and equipment in accounts payable	12	446	0
Change in common stock warrant liability associated with exercise of warrants	(916)	(79)	0
Warrants issued in connection with public offering	0	0	20,959
Asset retirement obligation	0	0	286
Warrants issued in connection with debt	$ 558	$ 0	$ 0