CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net income	$ 22,797	$ 23,465
Adjustments to reconcile net income to net cash provided by operations:
Stock-based compensation	10,761	10,101
Amortization of interest income	1,106	1,194
Depreciation and amortization of property and equipment	288	254
Deferred income taxes	(9,935)	(5,360)
Non-cash amortization of right-of-use asset	514	489
Changes in operating assets and liabilities:
Trade receivables	447	3,998
Inventory	(163)	866
Prepaid expenses and other current assets	(9)	(2,850)
Accounts payable	2,256	(3,493)
Accrued research and development expenses	609	(138)
Accrued and other liabilities	4,995	(3,217)
Long-term accrued income taxes	2,107	597
Operating lease liability	(526)	(484)
Net cash provided by operating activities	35,247	25,422
Cash flows from investing activities:
Purchases of property and equipment	(12)	(126)
Proceeds from maturities of marketable securities	42,127	124,230
Purchases of marketable securities	(92,611)	(127,388)
Net cash used in investing activities	(50,496)	(3,284)
Cash flows from financing activities:
Proceeds from exercise of stock options, net of issuance costs	1,382	4,038
Repurchase of common stock	0	(33,541)
Cash paid to satisfy statutory withholding requirement for net settlement of cashless option exercises	(1,888)	(16,444)
Net cash used in financing activities	(506)	(45,947)
Net decrease in cash and cash equivalents	(15,755)	(23,809)
Cash and cash equivalents, at beginning of period	77,617	76,190
Cash and cash equivalents, at end of period	61,862	52,381
Supplemental disclosure:
Cost of shares repurchased for net settlement of cashless option exercises	5,149	6,045
Recognition of right-of-use asset and lease liability	$ 2,816	$ 0