CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Operating activities:
Net income (loss)	$ (43,769)		$ (10,012)	$ (102,249)	$ 80,873
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation				6,360	6,253
Amortization of right-of-use operating lease assets				784	1,035
Amortization of patents				999	948
Amortization of premium (discount) on investments, net				3,842	(5,163)
Amortization of debt issuance costs				1,236	957
Amortization of convertible senior notes discount				17,807	17,661
Stock-based compensation expense				89,233	87,437
Gain on investments	(9,625)		0	(9,887)	0
Non-cash losses related to patents, licensing and property, plant and equipment and investments				211	203
Provision for deferred income taxes				(2,513)	14,436
Changes in operating assets and liabilities:
Contracts receivable				35,200	(16,255)
Inventories				(3,018)	(5,736)
Other current and long-term assets				1,064	(6,372)
Accounts payable				(14,939)	(16,104)
Accrued compensation				(14,535)	(9,219)
Other current liabilities				(1,968)	3,283
Deferred contract revenue				(59,355)	(73,643)
Net cash provided by (used in) operating activities				(51,728)	80,594
Investing activities:
Purchases of short-term investments				(976,284)	(1,049,274)
Proceeds from sale of short-term investments				982,173	877,966
Purchases of property, plant and equipment				(18,178)	(7,243)
Acquisition of licenses and other assets, net				(3,023)	(2,310)
Net cash used in investing activities				(15,312)	(180,861)
Financing activities:
Proceeds from issuance of equity, net				16,453	102,004
Payments of tax withholdings related to vesting of employee stock awards and exercise of employee stock options				(11,971)	(8,034)
Repurchases and retirements of common stock		$ (90,600)		(90,548)	0	$ (34,400)
Net cash provided by (used in) financing activities				(86,066)	93,970
Net increase in cash and cash equivalents				(153,106)	(6,297)
Cash and cash equivalents at beginning of period		$ 683,287		683,287	278,820	278,820
Cash and cash equivalents at end of period	$ 530,181		$ 272,523	530,181	272,523	$ 683,287
Supplemental disclosures of cash flow information:
Interest paid				3,093	4,776
Income taxes paid				49	0
Supplemental disclosures of non-cash investing and financing activities:
Right-of-use assets obtained in exchange for lease liabilities				0	13,920
Amounts accrued for capital and patent expenditures				$ 6,461	$ 3,073