CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities
Net income (loss)	$ (43,032)	$ 347,099
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Intangible asset amortization	125,821	118,461
Share-based compensation	59,258	55,841
Impairment charge	136,139	0
Depreciation	9,266	6,894
Acquired in-process research and development	205,250	58,200
Deferred tax benefit	(82,768)	(151,347)
Provision for losses on accounts receivable and inventory	4,078	2,403
Loss on extinguishment of debt	4,475	0
Amortization of debt discount and deferred financing costs	24,793	22,584
Other non-cash transactions	3,496	(779)
Changes in assets and liabilities:
Accounts receivable	3,640	(47,574)
Inventories	(18,826)	(18,562)
Prepaid expenses and other current assets	(44,853)	(15,929)
Other non-current assets	1,982	(1,067)
Operating lease assets	6,422	7,399
Accounts payable	5,264	(14,096)
Accrued liabilities	(6,972)	(59,031)
Income taxes payable	45,481	29,050
Deferred revenue	(2,360)	(3,054)
Other non-current liabilities	25,912	14,177
Operating lease liabilities, less current portion	(6,978)	431
Net cash provided by operating activities	455,488	351,100
Investing activities
Proceeds from maturity of investments	565,000	630,000
Purchases of property, plant and equipment	(7,520)	(21,911)
Acquired in-process research and development	(205,250)	(58,200)
Acquisition of intangible assets	(113,000)	(25,500)
Acquisition of investments	(1,040,475)	(360,975)
Net cash provided by (used in) investing activities	(801,245)	163,414
Financing activities
Net proceeds from issuance of Exchangeable Senior Notes, due 2026	981,381	0
Proceeds from revolving credit facility	500,000	0
Proceeds from employee equity incentive and purchase plans	24,251	16,122
Payment of employee withholding taxes related to share-based awards	(14,663)	(14,813)
Repayments of long-term debt	(16,693)	(16,693)
Share repurchases	(146,537)	(171,118)
Payments for partial repurchase of Exchangeable Senior Notes, due 2021	(332,888)	0
Repayments under revolving credit facility	(500,000)	0
Net cash provided by (used in) financing activities	494,851	(186,502)
Effect of exchange rates on cash and cash equivalents	(356)	105
Net increase in cash and cash equivalents	148,738	328,117
Cash and cash equivalents, at beginning of period	637,344	309,622
Cash and cash equivalents, at end of period	$ 786,082	$ 637,739