CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Operating activities:
Net loss	$ (170,300)	$ (170,744)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	7,484	7,951
Amortization of right-of-use operating lease assets	1,300	781
Amortization of patents	1,197	1,137
Amortization of premium on investments, net	7,867	8,824
Amortization of debt issuance costs	2,688	2,193
Stock-based compensation expense	50,738	67,882
Loss (gain) on investments	54	(873)
Loss on early retirement of debt	0	8,627
Non-cash losses related to disposal of property, plant and equipment	527	0
Non-cash losses related to patents	951	827
Changes in operating assets and liabilities:
Contracts receivable	55,145	52,200
Inventories	4,995	(2,134)
Other current and long-term assets	(39)	9,179
Income taxes payable	(22)	551
Accounts payable	(2,672)	(2,819)
Accrued compensation	(13,825)	(35,506)
Accrued liabilities and other current liabilities	45,170	(14,914)
Deferred contract revenue	(41,004)	(50,476)
Net cash used in operating activities	(49,746)	(117,314)
Investing activities:
Purchases of short-term investments	(663,195)	(740,721)
Proceeds from sale of short-term investments	380,375	727,859
Purchases of property, plant and equipment	(6,040)	(6,130)
Acquisition of licenses and other assets, net	(1,993)	(3,182)
Net cash used in nvesting activities	(290,853)	(22,174)
Financing activities:
Proceeds from equity, net	3,462	9,642
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options	(9,572)	(15,795)
Proceeds from the issuance of 0 percent convertible notes	0	632,500
0 percent convertible senior notes issuance costs	0	(15,551)
Repurchase of $247.9 million principal amount of the 1 percent convertible senior notes	0	(256,963)
Proceeds from issuance of warrants	0	89,752
Purchase of note hedges	0	(136,620)
Net cash (used in) provided by financing activities	(6,110)	306,965
Effects of exchange rates on cash	(565)	(22)
Net (decrease) increase in cash and cash equivalents	(347,274)	167,455
Cash and cash equivalents at beginning of period	869,191	397,664
Cash and cash equivalents at end of period	521,917	565,119
Supplemental disclosures of cash flow information:
Interest paid	1,544	2,866
Income taxes paid	2	0
Supplemental disclosures of non-cash investing and financing activities:
Amounts accrued for capital and patent expenditures	$ 1,121	$ 278