Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net income	$ 75,881	$ 431,229
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	715	806
Loss on disposal of property and equipment		17
Share-based compensation expense	12,690	9,985
Change in fair value of note hedge warrants	(1,164)	(1,027)
Change in fair value of convertible note hedges	1,115	1,803
Non-cash interest expense	1,053	11,750
Deferred income taxes (including benefit from valuation allowance release)	29,594	(337,800)
Changes in assets and liabilities:
Accounts receivable, net	21,394	19,794
Prepaid expenses and other current assets	(1,264)	(3,101)
Operating lease right-of-use assets	650	601
Other assets	128	64
Accounts payable and accrued expenses	(10,765)	(10,428)
Accrued research and development costs	(9,558)	(260)
Operating lease liabilities	(978)	(891)
Other liabilities	5,998	(280)
Net cash provided by operating activities	125,489	122,262
Cash flows from investing activities:
Purchases of property and equipment	(97)
Net cash (used in) investing activities	(97)
Cash flows from financing activities:
Proceeds from exercise of stock options and employee stock purchase plan	5,937	7,873
Payment on 2022 Convertible Notes	(120,699)
Repurchases of common stock	(126,394)
Net cash provided by (used in) financing activities	(241,156)	7,873
Net increase in cash, cash equivalents and restricted cash	(115,764)	130,135
Cash, cash equivalents and restricted cash, beginning of period	621,864	364,784
Cash, cash equivalents and restricted cash, end of period	$ 506,100	$ 494,919