CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 76,406	$ 84,783
Available-for-sale securities	175,115	184,736
Accounts receivable, net	8,441	9,478
Inventories	15,628	16,186
Prepaid expenses and other assets	5,333	8,251
Total current assets	280,923	303,434
Property and equipment, net	670	788
Non-current assets	1,198	1,554
Total assets	282,791	305,776
Current liabilities:
Accounts payable	4,384	4,707
Accrued and other liabilities	20,357	15,686
Deferred revenue	1,694	19,174
Current portion of long-term debt	24,601	8,708
Total current liabilities	51,036	48,275
Long-term debt, net of current portion	220,183	232,610
Deferred revenue, net of current portion	5,732	6,449
Non-current accrued and other liabilities	369	257
Total liabilities	277,320	287,591
Commitments and contingencies
Stockholders' equity
Preferred stock; $1.00 par value; 5,000 shares authorized; no shares issued and outstanding at June 30, 2017 and December 31, 2016	0	0
Common stock; $.001 par value; 200,000 shares authorized; 105,759 and 104,874 shares issued and outstanding at June 30, 2017 and December 31, 2016, respectively	105	105
Additional paid-in capital	833,244	831,750
Accumulated other comprehensive loss	(382)	(616)
Accumulated deficit	(827,496)	(813,054)
Total stockholders' equity	5,471	18,185
Total liabilities and stockholders' equity	$ 282,791	$ 305,776