CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income	$ 80,459	$ 80,017
Adjustments to reconcile net income to net cash provided by operations:
Stock-based compensation	32,121	25,109
Deferred income taxes	2,047	11,778
Amortization of interest income	3,805	404
Depreciation and amortization of property and equipment	783	447
Non-cash amortization of right-of-use asset	1,487	1,228
Others	0	148
Changes in operating assets and liabilities:
Trade receivables	(310)	(2,029)
Inventory	2,655	694
Prepaid expenses and other current assets	(2,288)	(1,882)
Other assets	894	(1,562)
Accounts payable	(3,961)	(988)
Accrued clinical expenses	(860)	9,055
Accrued and other liabilities	3,138	(4,315)
Operating lease liability	(1,505)	(1,205)
Net cash provided by operating activities	118,465	116,899
Cash flows from investing activities:
Purchases of property and equipment	(404)	(807)
Proceeds from maturities of marketable securities	308,864	193,418
Purchases of marketable securities	(312,805)	(323,094)
Net cash used in investing activities	(4,345)	(130,483)
Cash flows from financing activities:
Proceeds from exercise of stock options, net of issuance costs	13,182	13,240
Repurchase of common stock	(88,485)	(275)
Cash paid to satisfy statutory withholding requirement for net settlement of cashless option exercises	(20,319)	(90)
Net cash (used in) provided by financing activities	(95,622)	12,875
Net increase (decrease) in cash and cash equivalents	18,498	(709)
Cash and cash equivalents, at beginning of period	76,190	31,269
Cash and cash equivalents, at end of period	94,688	30,560
Supplemental disclosure:
Cost of shares repurchased for net settlement of cashless option exercises	9,705	900
Recognition of right-of-use asset and lease liability	$ 0	$ 775