Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 1,176,810	$ 2,087,103	$ 91,635
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	360,489	325,047	293,236
Depreciation expense	106,941	72,420	61,397
Deferred income taxes (including benefit from valuation allowance release in 2018)	167,387	(1,512,325)	(120,513)
Gains on equity securities	(197,597)	(2,558)	0
Increase in fair value of contingent consideration	4,459	0	0
Intangible asset impairment charges	0	29,000	255,340
Acquired in-process research and development	0	0	160,000
Deconsolidation of VIE	0	1,077	76,644
Other non-cash items, net	16,942	32,502	14,439
Changes in operating assets and liabilities:
Accounts receivable, net	(225,587)	(108,152)	(71,759)
Inventories	(64,047)	(31,965)	(47,484)
Prepaid expenses and other assets	35,440	16,684	(111,063)
Accounts payable	(22,785)	36,554	8,753
Accrued expenses	172,881	302,755	255,178
Other liabilities	37,997	22,144	(20,861)
Net cash provided by operating activities	1,569,330	1,270,286	844,942
Cash flows from investing activities:
Payments to acquire businesses, net of cash acquired	(1,154,212)	0	0
Purchases of available-for-sale debt securities	(537,196)	(431,918)
Purchases of available-for-sale debt securities			(532,581)
Maturities of available-for-sale debt securities	475,924	431,576	369,214
Sale of equity securities	94,936	0	0
Expenditures for property and equipment	(75,451)	(95,524)	(99,421)
Investment in equity securities	(39,319)	(83,471)	0
Investment in note receivable	0	(15,000)	0
Decrease in restricted cash due to deconsolidation of VIE		(7,896)	(61,602)
Purchase of in-process research and development	0	0	(160,000)
Other investing activities	0	75	1,061
Net cash used in investing activities	(1,235,318)	(202,158)	(483,329)
Cash flows from financing activities:
Issuances of common stock under benefit plans	343,244	289,293	344,840
Repurchases of common stock	(192,015)	(350,043)	0
Payments on finance leases	(39,185)
Advance from collaborator	12,500	7,500	12,500
Proceeds related to capital lease and construction financing lease obligations	10,046	20,840	34,666
Repayments of advanced funding	(5,866)	(5,027)	(4,266)
Payments on capital lease and construction financing lease obligations	0	(33,388)	(19,336)
Payments on revolving credit facility	0	0	(300,000)
Other financing activities	(1,951)	(394)	0
Net cash provided by (used in) financing activities	126,773	(71,219)	68,404
Effect of changes in exchange rates on cash	1,643	(6,182)	5,802
Net increase in cash, cash equivalents and restricted cash	462,428	990,727	435,819
Cash, cash equivalents and restricted cash—beginning of period	2,658,253	1,667,526	1,231,707
Cash, cash equivalents and restricted cash—end of period	3,120,681	2,658,253	1,667,526
Supplemental disclosure of cash flow information:
Cash paid for interest	55,554	66,458	68,696
Cash paid for income taxes	24,730	12,402	6,414
Capitalization of costs related to construction financing lease obligation	0	3,389	40,855
Issuances of common stock from employee benefit plans receivable	$ 2,820	$ 86	$ 844