CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities:
Net loss	$ (65,165)	$ (89,869)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	3,701	3,917
Amortization of right-of-use operating lease assets	602	394
Amortization of patents	592	544
Amortization of premium on investments, net	4,175	4,023
Amortization of debt issuance costs	1,343	860
Stock-based compensation expense	26,236	37,861
Gain on investments	(10)	(13)
Non-cash losses related to disposal of property, plant and equipment	527	0
Non-cash losses related to patents	110	221
Changes in operating assets and liabilities:
Contracts receivable	35,774	52,807
Inventories	774	(234)
Other current and long-term assets	(7,222)	16,481
Income taxes receivable	865	2
Accounts payable	2,878	(9,569)
Accrued compensation	(22,285)	(36,465)
Accrued liabilities and other current liabilities	10,473	(11,905)
Deferred contract revenue	(25,018)	(23,717)
Net cash used in operating activities	(31,650)	(54,662)
Investing activities:
Purchases of short-term investments	(462,855)	(330,051)
Proceeds from sale of short-term investments	178,837	411,907
Purchases of property, plant and equipment	(2,705)	(1,772)
Acquisition of licenses and other assets, net	(826)	(1,228)
Net cash (used in) provided by investing activities	(287,549)	78,856
Financing activities:
Proceeds from equity, net	1,848	7,760
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options	(9,173)	(15,337)
Net cash used in financing activities	(7,325)	(7,577)
Effects of exchange rates on cash	(154)	(126)
Net (decrease) increase in cash and cash equivalents	(326,678)	16,491
Cash and cash equivalents at beginning of period	869,191	397,664
Cash and cash equivalents at end of period	542,513	414,155
Supplemental disclosures of cash flow information:
Interest paid	594	594
Income taxes paid	2	2
Supplemental disclosures of non-cash investing and financing activities:
Amounts accrued for capital and patent expenditures	$ 1,344	$ 1,876