Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (116,445)	$ (67,865)	$ (86,350)
Adjustments to reconcile loss to net cash used in operating activities:
Depreciation and amortization	23	62	138
Loss on sale of fixed assets			48
Allowance for doubtful accounts			12
Stock-based compensation	18,806	13,960	13,613
Amortization of debt discount and debt issuance costs	2,183	2,332	7,783
Amortization of intangible asset	646	646	645
Gain on change in fair value of derivative liabilities			(8,170)
Deferred income taxes		11,082	8,798
Changes in assets and liabilities:
Accounts receivable, net	(21,205)	(25,333)	(6,171)
Inventory	(27,542)	(9,753)	(1,522)
Prepaid and other current assets	510	6,028	(3,831)
Other long-term assets		567	(567)
Accrued interest payable	(310)	(6,491)	(6,205)
Deferred revenue	1,656	1,221	884
Accounts payable and other current liabilities	37,602	40,267	8,705
Other long-term liabilities	9,373	440	375
Net cash used in operating activities	(94,703)	(32,837)	(71,815)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of equipment	(58)	(12)	(21)
Net cash used in investing activities	(58)	(12)	(21)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of exchangeable debt		30,000
Proceeds from issuance of common stock, net of transaction costs	264,840		64,613
Proceeds from issuance of common stock under employee stock purchase plan	1,043
Proceeds from exercise of stock options, net of transaction costs	26,402	638	287
Payment of debt issuance costs		(1,207)
Payment of transaction costs for conversion of preferred stock	(39)
Repurchase of exchangeable senior notes, including transaction costs		(15,107)
Payment on long-term debt from royalty-bearing instrument	(14,690)	(3,322)
Transaction costs related to exchange of exchangeable senior notes	(121)		(680)
Taxes paid related to stock-based awards	(6,184)	(2,767)	(1,094)
Net cash provided by financing activities	271,251	8,235	63,126
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	176,490	(24,614)	(8,710)
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF PERIOD	74,237	98,851	107,561
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, END OF PERIOD	250,727	74,237	98,851
Cash paid during the year for:
Interest	21,527	17,241	17,083
Income taxes	850	$ 1,753	1,457
Supplemental disclosure of non-cash transactions:
Exchange of exchangeable senior notes into common stock	29,490		$ 128,115
Conversion of Series A Convertible Preferred Stock into common stock	$ 2,514