CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities
Net income	$ 15,147	$ 111,337
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	1,043	1,022
Stock-based compensation	10,148	9,790
Amortization of premiums and accretion of discounts on marketable securities	(175)	(2,627)
Gain on sale of marketable securities	(229)	0
Intangible asset amortization	1,108	1,135
Deferred income taxes	3,793	(89,155)
Other non-cash adjustments, net	1,361	1,517
Changes in operating assets and liabilities:
Accounts receivable	(1,774)	1,914
Prepaid expenses and other assets	2,897	(2,956)
Inventory	(3,128)	(896)
Accounts payable and other liabilities	1,408	3,191
Product revenue allowances	874	1,884
Net cash provided by operating activities	32,473	36,156
Cash flows from investing activities
Purchases of property and equipment	(829)	(951)
Purchases of marketable securities	(264,112)	(291,333)
Sales and maturities of marketable securities	240,128	230,205
Net cash used in investing activities	(24,813)	(62,079)
Cash flows from financing activities
Proceeds from the exercise of stock options	4,202	4,148
Net cash provided by financing activities	4,202	4,148
Effect of exchange rate changes on cash, cash equivalents and restricted cash	41	(24)
Net change in cash, cash equivalents and restricted cash	11,903	(21,799)
Cash, cash equivalents and restricted cash
Beginning of period	45,650	61,749
End of period	$ 57,553	$ 39,950