Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 87,935	$ 87,229
Marketable securities	129,913	171,555
Accounts receivable, net	15,130	13,121
Inventories	10,324	7,637
Prepaid expenses and other current assets	4,656	5,500
Total current assets	247,958	285,042
Property and equipment, net	10,329	10,710
Right-of-use assets	6,332
Total assets	264,619	295,752
Current liabilities
Accounts payable	11,007	12,340
Accrued expenses and other current liabilities	15,785	14,310
Operating lease liabilities	1,142
Current portion of long-term debt	11,280	9,967
Total current liabilities	39,214	36,617
Long-term operating lease liability, net	5,639
Long-term debt, net		3,640
2024 convertible notes, net	146,939	144,879
Other long-term liabilities	251	537
Total liabilities	192,043	185,673
Commitments and contingencies
Preferred stock, $0.001 par value; 10,000,000 shares authorized at March 31, 2019 and December 31, 2018 and 0 shares issued and outstanding at March 31, 2019 and December 31, 2018	0	0
Stockholders' equity
Common stock, $0.001 par value; 100,000,000 shares authorized; 37,992,631 and 37,946,341 shares issued and outstanding, at March 31, 2019 and December 31, 2018, respectively	38	38
Additional paid-in capital	632,797	628,944
Accumulated other comprehensive income (loss)	105	(77)
Accumulated deficit	(560,364)	(518,826)
Total stockholders' equity	72,576	110,079
Total liabilities and stockholders' equity	$ 264,619	$ 295,752