CONDENSED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Operating activities
Net income (loss)	$ 450	$ (9,700)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Amortization expense	10,295	3,688	$ 14,752
Depreciation expense	198	184
Stock-based compensation expense	4,951	4,263
Non-cash lease expense	18	114
Non-cash interest expense for amortization of debt discount and issuance costs	1,336
Changes in operating assets and liabilities:
Accounts receivable	(12,474)	(7,193)
Inventory	(6,714)	(924)
Prepaid expenses and other assets	(2,990)	76
Accounts payable	(108)	1,583
Accrued expenses	(15,968)	(8,263)
Accrued rebates, returns and discounts	14,337	7,545
Operating lease assets and liabilities		734
Other long-term liabilities		(676)
Net cash used in operating activities	(6,669)	(8,569)
Investing activities
Purchase of intangible asset	(366,811)
Purchases of property and equipment	(836)	(3,323)
Net cash used in investing activities	(367,647)	(3,323)
Financing activities
Proceeds from issuances of common stock from employee stock purchase plans	357	444
Proceeds from the exercise of stock options	4,454	213
Payments made for employee restricted stock tax withholdings	(1,358)	(488)
Proceeds from issuance of term note, net of issuance costs of $2,200	192,373
Proceeds from convertible senior notes, net of issuance costs of $4,956	138,794
Repayment of term loan	(11,500)
Net cash provided by financing activities	323,120	169
Net decrease in cash, cash equivalents and restricted cash	(51,196)	(11,723)
Cash, cash equivalents and restricted cash at beginning of period	170,019	146,633	146,633
Cash, cash equivalents and restricted cash at end of period	118,823	134,910	170,019
Reconciliation of cash, cash equivalents and restricted cash to the condensed consolidated balance sheets:
Cash and cash equivalents				$ 116,178	$ 170,019	$ 134,910
Restricted cash				2,645
Total cash, cash equivalents and restricted cash	118,823	134,910	$ 146,633	$ 118,823	$ 170,019	$ 134,910
Supplemental disclosure of cash flow information
Cash paid for interest	3,456	178
Supplemental disclosure of non-cash activities
Acquisition of property and equipment in accounts payable and accrued expenses	392	810
Asset acquisition transaction costs in accounts payable and accrued expenses	1,415
Accrued royalties discharged upon closing of asset acquisition	1,145
Inventory used in the construction and installation of property and equipment	394	0
Term notes issuance costs in accounts payable and accrued expenses	256
Convertible senior notes issuance costs in accounts payable and accrued expenses	$ 517
Receivable from stock option exercises in other current assets		33
Operating lease assets assumed		9,957
Operating lease liabilities assumed		$ 10,691