CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net loss	$ (18,652)	$ (23,078)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation expense	482	208
Amortization expense	29,526
Lease incentive obligation		(9)
Stock-based compensation expense	2,728	1,821
Non-cash interest expense	5,528
Changes in operating assets and liabilities:
Accounts receivable	(56,067)	(1,220)
Inventories	134	(179)
Prepaid expenses and other assets	(523)	(148)
Accounts payable	3,652	(2,313)
Accrued expenses	8,900	(2,521)
Accrued rebates, returns and discounts	53,955
Deferred revenue		3,751
Net cash provided by (used in) operating activities	29,663	(23,688)
Investing activities
Cash paid for asset acquisition	(18,761)
Purchases of property and equipment	(356)	(29)
Net cash used in investing activities	(19,117)	(29)
Financing activities
Cash paid for common stock offerings costs	(30)
Proceeds from issuances of common stock from employee stock purchase plans	510	673
Proceeds from term loan amendment, net of repayment of amended term loan	10,020
Repayment of asset acquisition obligations	(13,045)
Repayment of term note		(666)
Proceeds from the exercise of stock options	2,373	94
Payments made for employee restricted stock tax withholdings	(216)	(51)
Net cash (used in) provided by financing activities	(388)	50
Net increase (decrease) in cash, cash equivalents and restricted cash	10,158	(23,667)
Cash, cash equivalents and restricted cash at beginning of period	118,794	153,322
Cash, and cash equivalents and restricted cash at end of period	128,952	129,655
Supplemental disclosure of cash flow information
Cash paid for offering costs	30
Cash paid for interest	109	49
Supplemental disclosure of non-cash activities
Offering costs in accrued expenses	25	112
Acquisition of property and equipment in accrued expenses	129	$ 99
Asset acquisition transaction costs in accrued expenses	116
Liabilities assumed from asset acquisition in accrued rebates, returns and discounts	$ 22,660