BioMarin Pharmaceutical (BMRN) 10-Q 6 Nov 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 23, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	000-26727
Entity Registrant Name	BioMarin Pharmaceutical Inc
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	68-0397820
Entity Address, Address Line One	770 Lindaro Street
Entity Address, City or Town	San Rafael
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94901
City Area Code	415
Local Phone Number	506-6700
Title of 12(b) Security	Common Stock, par value $0.001
Trading Symbol	BMRN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		181,529,667
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001048477
Current Fiscal Year End Date	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	[1]
Current assets:
Cash and cash equivalents	$ 1,015,675	$ 437,446
Short-term investments	489,998	316,361
Accounts receivable, net	411,712	377,404
Inventory	700,847	680,275
Other current assets	120,747	130,657
Total current assets	2,738,979	1,942,143
Noncurrent assets:
Long-term investments	265,122	411,978
Property, plant and equipment, net	1,015,062	1,010,868
Intangible assets, net	427,172	456,580
Goodwill	196,199	197,039
Deferred tax assets	1,396,547	549,422
Other assets	119,009	122,009
Total assets	6,158,090	4,690,039
Current liabilities:
Accounts payable and accrued liabilities	480,403	570,621
Short-term convertible debt, net	374,290	361,882
Total current liabilities	854,693	932,503
Noncurrent liabilities:
Long-term convertible debt, net	1,074,164	486,238
Long-term contingent consideration	54,103	50,793
Other long-term liabilities	121,237	98,124
Total liabilities	2,104,197	1,567,658
Stockholders’ equity:
Common stock, $0.001 par value: 500,000,000 shares authorized; 181,492,344 and 179,838,114 shares issued and outstanding, respectively.	181	180
Additional paid-in capital	4,937,791	4,832,707
Company common stock held by Nonqualified Deferred Compensation Plan (the NQDC)	(10,756)	(9,961)
Accumulated other comprehensive income	10,385	20,164
Accumulated deficit	(883,708)	(1,720,709)
Total stockholders’ equity	4,053,893	3,122,381	[2]
Total liabilities and stockholders’ equity	$ 6,158,090	$ 4,690,039
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.
[2]	The beginning balances for the nine-month periods were derived from the audited Consolidated Financial Statements included in Company’s Annual Report on Form 10-K for the years ended December 31, 2019 and 2018, respectively, filed with the SEC on February 27, 2020.

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	181,492,344	179,838,114
Common stock, shares outstanding (in shares)	181,492,344	179,838,114

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
REVENUES:
Total revenues	$ 476,784	$ 461,097	$ 1,408,338	$ 1,249,605
OPERATING EXPENSES:
Cost of sales	188,793	96,949	398,134	263,567
Research and development	147,053	172,963	471,449	542,195
Selling, general and administrative	179,450	170,112	542,157	493,024
Intangible asset amortization and contingent consideration	17,429	17,063	48,018	57,114
Gain on sale of nonfinancial assets	0	0	(59,495)	(15,000)
Total operating expenses	532,725	457,087	1,400,263	1,340,900
INCOME (LOSS) FROM OPERATIONS	(55,941)	4,010	8,075	(91,295)
Equity in the loss of BioMarin/Genzyme LLC	(921)	(551)	(1,077)	(780)
Interest income	4,004	5,340	13,539	17,537
Interest expense	(9,597)	(2,937)	(24,560)	(16,530)
Other income, net	1,239	3,960	1,886	6,038
INCOME (LOSS) BEFORE INCOME TAXES	(61,216)	9,822	(2,137)	(85,030)
Benefit from income taxes	(846,019)	(45,214)	(839,138)	(46,158)
NET INCOME (LOSS)	$ 784,803	$ 55,036	$ 837,001	$ (38,872)
NET INCOME (LOSS) PER SHARE, BASIC (in dollars per share)	$ 4.33	$ 0.31	$ 4.63	$ (0.22)
NET INCOME (LOSS) PER SHARE, DILUTED (in dollars per share)	$ 4.01	$ 0.30	$ 4.39	$ (0.22)
Weighted average common shares outstanding, basic (in shares)	181,142	179,289	180,592	178,873
Weighted average common shares outstanding, diluted (in shares)	197,674	185,924	194,959	178,873
COMPREHENSIVE INCOME (LOSS)	$ 765,138	$ 74,600	$ 827,222	$ (7,140)
Net product revenues
REVENUES:
Total revenues	460,741	450,900	1,368,816	1,224,458
Royalty and other revenues
REVENUES:
Total revenues	$ 16,043	$ 10,197	$ 39,522	$ 25,147

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands		Total		Common Stock		Additional Paid-in Capital		Treasury Stock		Company Stock Held By NQDC		Accumulated other comprehensive income (loss)		Accumulated Deficit		Accumulated DeficitImpact of change in accounting principles
Beginning balance (in shares) at Dec. 31, 2018	[1]			178,253
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				1,351
Repurchase of common stock (in shares)				0
Ending balance (in shares) at Sep. 30, 2019				179,604
Beginning balance at Dec. 31, 2018		$ 2,967,940	[1]	$ 178	[1]	$ 4,669,926	[1]	$ 0	[1]	$ (13,301)	[1]	$ 5,271	[1]	$ (1,694,134)	[1]	$ (2,727)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				2		(19,183)
Stock-based compensation						122,212
Repurchase of common stock						0		0
Common stock held by the NQDC						(692)				692
Retirement of treasury stock								0
Accounting impact of NQDC Plan change						10,653				2,648
Other comprehensive income (loss)												31,732
Net income (loss)		(38,872)												(38,872)
Ending balance at Sep. 30, 2019		3,074,405		$ 180		4,782,916		0		(9,961)		37,003		(1,735,733)
Beginning balance (in shares) at Jun. 30, 2019	[1]			179,433
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				171
Repurchase of common stock (in shares)				0
Ending balance (in shares) at Sep. 30, 2019				179,604
Beginning balance at Jun. 30, 2019		2,960,954	[1]	$ 179	[1]	4,744,316	[1]	0	[1]	(10,211)	[1]	17,439	[1]	(1,790,769)	[1]	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				1		(1,294)
Stock-based compensation						40,144
Repurchase of common stock						0		0
Common stock held by the NQDC						(250)				250
Retirement of treasury stock								0
Accounting impact of NQDC Plan change						0				0
Other comprehensive income (loss)												19,564
Net income (loss)		55,036												55,036
Ending balance at Sep. 30, 2019		3,074,405		$ 180		4,782,916		0		(9,961)		37,003		(1,735,733)
Beginning balance (in shares) at Dec. 31, 2019	[1]			179,838
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				2,172
Repurchase of common stock (in shares)				(518)
Ending balance (in shares) at Sep. 30, 2020				181,492
Beginning balance at Dec. 31, 2019		3,122,381	[1],[2]	$ 180	[1]	4,832,707	[1]	0	[1]	(9,961)	[1]	20,164	[1]	(1,720,709)	[1]	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				1		17,601
Stock-based compensation						136,688
Repurchase of common stock						(50,000)		(50,000)
Common stock held by the NQDC						795				(795)
Retirement of treasury stock								50,000
Accounting impact of NQDC Plan change						0				0
Other comprehensive income (loss)												(9,779)
Net income (loss)		837,001												837,001
Ending balance at Sep. 30, 2020		4,053,893		$ 181		4,937,791		0		(10,756)		10,385		(883,708)
Beginning balance (in shares) at Jun. 30, 2020	[1]			181,148
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				344
Repurchase of common stock (in shares)				0
Ending balance (in shares) at Sep. 30, 2020				181,492
Beginning balance at Jun. 30, 2020		3,236,679	[1]	$ 181	[1]	4,885,637	[1]	0	[1]	(10,678)	[1]	30,050	[1]	(1,668,511)	[1]	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				0		7,319
Stock-based compensation						44,757
Repurchase of common stock						0		0
Common stock held by the NQDC						78				(78)
Retirement of treasury stock								0
Accounting impact of NQDC Plan change						0				0
Other comprehensive income (loss)												(19,665)
Net income (loss)		784,803												784,803
Ending balance at Sep. 30, 2020		$ 4,053,893		$ 181		$ 4,937,791		$ 0		$ (10,756)		$ 10,385		$ (883,708)
[1]	The beginning balances for the nine-month periods were derived from the audited Consolidated Financial Statements included in Company’s Annual Report on Form 10-K for the years ended December 31, 2019 and 2018, respectively, filed with the SEC on February 27, 2020.
[2]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 837,001	$ (38,872)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	77,814	79,510
Non-cash interest expense	14,766	9,395
Amortization of premium (accretion of discount) on investments	175	(1,897)
Stock-based compensation	142,125	121,763
Gain on sale of nonfinancial assets	(59,495)	(15,000)
Inventory write-off, net of stock-based compensation	75,609	0
Deferred income taxes	(854,199)	(59,780)
Unrealized foreign exchange loss	9,082	784
Non-cash changes in the fair value of contingent consideration	1,352	5,646
Other	388	(18)
Changes in operating assets and liabilities:
Accounts receivable, net	(32,915)	(61,803)
Inventory	(73,310)	(52,571)
Other current assets	32,848	(13,259)
Other assets	(5,543)	(7,112)
Accounts payable and accrued liabilities	(76,174)	21,747
Other long-term liabilities	9,225	2,386
Net cash provided by (used in) operating activities	98,749	(9,081)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	(83,286)	(94,241)
Maturities and sales of investments	345,224	635,678
Purchases of available-for-sale securities	(369,942)	(528,497)
Proceeds from sale of nonfinancial assets	67,159	15,000
Purchase of intangible assets	(14,369)	(8,323)
Investment in convertible note	(8,709)	0
Other	(725)	(1,747)
Net cash provided by (used in) investing activities	(64,648)	17,870
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercises of awards under equity incentive plans	60,268	21,768
Taxes paid related to net share settlement of equity awards	(42,667)	(40,951)
Payment of contingent acquisition consideration	0	(57,508)
Repurchase of common stock	(50,000)	0
Proceeds from convertible senior subordinated note offering, net	585,752	0
Principal repayments of financing leases	(6,080)	(2,025)
Net cash provided by (used in) financing activities	547,273	(78,716)
Effect of exchange rate changes on cash	(3,145)	(835)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	578,229	(70,762)
Cash and cash equivalents:
Beginning of period	437,446	493,982
End of period	1,015,675	423,220
SUPPLEMENTAL CASH FLOW DISCLOSURES:
Cash paid for income taxes	4,355	6,088
Cash paid for interest	5,615	5,777
SUPPLEMENTAL CASH FLOW DISCLOSURES FOR NON-CASH INVESTING AND FINANCING ACTIVITIES:
Decrease in accounts payable and accrued liabilities related to fixed assets	(13,281)	(5,801)
Increase (decrease) in accounts payable and accrued liabilities related to intangible assets	$ (3,043)	$ 2,053

NATURE OF OPERATIONS

NATURE OF OPERATIONS	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
NATURE OF OPERATIONS	NATURE OF OPERATIONS BioMarin Pharmaceutical Inc. (the Company) is a global biotechnology company that develops and commercializes innovative therapies for people with serious and life-threatening rare diseases and medical conditions. The Company selects product candidates for diseases and conditions that represent a significant unmet medical need, have well-understood biology and provide an opportunity to be first-to-market or offer a significant benefit over existing products. The Company’s portfolio consists of several commercial therapies and multiple clinical and preclinical product candidates. The Company expects to continue to finance future cash needs that exceed its operating activities primarily through its current cash, cash equivalents and investments and through proceeds from debt or equity offerings, commercial borrowing, or through collaborative agreements with corporate partners. If the Company elects to increase its spending on development programs significantly above current long-term plans or enters into potential licenses and other acquisitions of complementary technologies, products or companies, the Company may need additional capital.

BASIS OF PRESENTATION

BASIS OF PRESENTATION	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION The accompanying Condensed Consolidated Financial Statements have been prepared pursuant to United States (U.S.) generally accepted accounting principles (U.S. GAAP) and the rules and regulations of the SEC for Quarterly Reports on Form 10-Q and do not include all of the information and note disclosures required by U.S. GAAP for complete financial statements, although the Company believes that the disclosures herein are adequate to ensure that the information presented is not misleading. The Condensed Consolidated Financial Statements should therefore be read in conjunction with the Consolidated Financial Statements and Notes thereto for the fiscal year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2020 or any other period. On January 1, 2020, the Company adopted Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13), as amended, using a modified retrospective approach. The standard has amended the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the incurred-loss model with an expected-loss model. This new standard also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income rather than by reducing the carrying amount under the current, other-than-temporary impairment model. Results for reporting periods beginning January 1, 2020 are presented under ASU 2016-13 and the adoption of this standard had no impact on the Company’s Financial Statements. U.S. GAAP requires management to make estimates and assumptions that affect amounts reported in the Condensed Consolidated Financial Statements and accompanying disclosures. Although these estimates are based on management’s best knowledge of current events and actions that the Company may undertake in the future, actual results may be different from those estimates. The Condensed Consolidated Financial Statements reflect all adjustments of a normal, recurring nature that are, in the opinion of management, necessary for a fair presentation of results for these interim periods. The full extent to which the novel coronavirus disease (referred to as COVID-19) pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including revenues, expenses, reserves and allowances, manufacturing, clinical trials and research and development costs, will depend on future developments that are highly uncertain at this time. As events continue to evolve and additional information becomes available, the Company’s estimates may change materially in future periods. Management performed an evaluation of the Company’s activities through the date of filing of this Quarterly Report on Form 10-Q, and has concluded that, except for the maturity and settlement of our convertible debt discussed in Note 12 - Debt , there were no subsequent events or transactions that occurred subsequent to the balance sheet date prior to filing this Quarterly Report on Form 10-Q that would require recognition or disclosure in the Condensed Consolidated Financial Statements.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES There have been no material changes to the Company’s significant accounting policies during the nine months ended September 30, 2020, as compared to the significant accounting policies disclosed in Note 3 – Significant Accounting Policies included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019.

RECENT ACCOUNTING PRONOUNCEMENT

RECENT ACCOUNTING PRONOUNCEMENTS	9 Months Ended
	Sep. 30, 2020
Accounting Standards Update and Change in Accounting Principle [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS Except as described in Note 2 – Basis of Presentation , there have been no new accounting pronouncements adopted by the Company or new accounting pronouncements issued by the FASB during the nine months ended September 30, 2020, as compared to the recent accounting pronouncements described in Note 4 of the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, that the Company believes are of significance or potential significance to the Company.

FINANCIAL INSTRUMENTS

FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
FINANCIAL INSTRUMENTS	FINANCIAL INSTRUMENTS All marketable securities were classified as available-for-sale at September 30, 2020 and December 31, 2019. The following tables show the Company’s cash, cash equivalents and available-for-sale securities by significant investment category for each period presented: September 30, 2020 Amortized Cost Gross Gross Aggregate Fair Value Cash and Cash Equivalents Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash $ 378,705 $ — $ — $ 378,705 $ 378,705 $ — $ — Level 2: Money market instruments 557,006 — — 557,006 557,006 — — Corporate debt securities 435,954 4,558 (14) 440,498 — 280,000 160,498 U.S. government agency securities 361,336 2,182 (1) 363,517 79,964 199,559 83,994 Asset-backed securities 23,430 129 — 23,559 — 3,639 19,920 Commercial paper 6,800 — — 6,800 — 6,800 — Foreign and other 549 161 — 710 — — 710 Subtotal 1,385,075 7,030 (15) 1,392,090 636,970 489,998 265,122 Total $ 1,763,780 $ 7,030 $ (15) $ 1,770,795 $ 1,015,675 $ 489,998 $ 265,122 December 31, 2019 Amortized Cost Gross Gross Aggregate Fair Value Cash and Cash Equivalents Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash $ 259,347 $ — $ — $ 259,347 $ 259,347 $ — $ — Level 2: Money market instruments 173,100 — — 173,100 173,100 — — Corporate debt securities 518,523 3,575 (12) 522,086 — 233,294 288,792 U.S. government agency securities 209,633 993 (67) 210,559 4,999 83,067 122,493 Foreign and other 549 145 (1) 693 — — 693 Subtotal 901,805 4,713 (80) 906,438 178,099 316,361 411,978 Total $ 1,161,152 $ 4,713 $ (80) $ 1,165,785 $ 437,446 $ 316,361 $ 411,978 (1) The Company’s short-term marketable securities mature in one year or less. (2) The Company’s long-term marketable securities mature between one As of September 30, 2020, the Company had the ability and intent to hold all investments that were in an unrealized loss position until maturity. The Company considered its intent and ability to hold the securities until recovery of amortized cost basis, the extent to which fair value is less than amortized cost basis, conditions specifically related to the security’s industry and geography, payment structure and history and changes to the ratings (if any) in determining that the decline in fair value compared to carrying value is not related to a credit loss.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	9 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS Intangible assets consisted of the following: September 30, December 31, Intangible assets: Finite-lived intangible assets $ 638,468 $ 652,734 Accumulated amortization (211,296) (196,154) Net carrying value $ 427,172 $ 456,580 In January 2020, the Company completed the sale of worldwide rights to Firdapse, the Company's commercial product for the treatment of Lambert-Eaton myasthenic syndrome, to a third party in exchange for a one-time cash payment of $67.2 million plus residual royalties. Under the terms of the agreement, the Company agreed to provide certain transition services to the third-party purchaser, such as customer sales and support, for up to 12 months after the closing of the transaction. During the first quarter of 2020, the Company recognized a before-tax net gain of $59.5 million related to the sale of the Firdapse intellectual property (IP) and existing inventory. Additionally, the Company recognized a $0.8 million reduction to goodwill and disposed of $32.2 million in intangible assets, including related accumulated amortization of $31.6 million, as a result of the sale of Firdapse. During the second quarter of 2019, the Company recorded $15.0 million of gain on sale of intangible assets, reported in Gain on Sale of Nonfinancial Assets in the Consolidated Statements of Comprehensive Income (Loss), due to a third party's achievement of a commercial sales milestone related to a previously sold intangible asset.

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment, net consisted of the following: September 30, December 31, Building and improvements $ 756,479 $ 725,906 Manufacturing and laboratory equipment 402,357 366,951 Computer hardware and software 187,722 167,554 Land 90,418 90,418 Leasehold improvements 52,479 51,324 Furniture and equipment 39,360 38,569 Land improvements 7,349 7,349 Construction-in-progress 92,581 111,897 1,628,745 1,559,968 Accumulated depreciation (613,683) (549,100) Total property, plant and equipment, net $ 1,015,062 $ 1,010,868 The construction-in-progress balance primarily included costs related to significant in-progress projects at the Company's facilities in Marin County, California, and Shanbally, Ireland. Three Months Ended Nine Months Ended 2020 2019 2020 2019 Depreciation expense $ 22,187 $ 24,238 $ 65,749 $ 67,206 Depreciation capitalized into inventory $ 10,883 $ 9,807 $ 34,053 $ 24,894

SUPPLEMENTAL BALANCE SHEET INFO

SUPPLEMENTAL BALANCE SHEET INFORMATION	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
SUPPLEMENTAL BALANCE SHEET INFORMATION	SUPPLEMENTAL BALANCE SHEET INFORMATION Inventory consisted of the following: September 30, December 31, Raw materials $ 73,857 $ 74,442 Work-in-process 296,685 349,978 Finished goods 330,305 255,855 Total inventory $ 700,847 $ 680,275 Valoctocogene roxaparvovec is an investigational gene therapy product candidate for the treatment of severe hemophilia A. The Company must receive marketing approval from the applicable regulators before the valoctocogene roxaparvovec inventory can be sold commercially. Starting in the second quarter of 2019, the Company believed that material uncertainties related to the ultimate regulatory approval of valoctocogene roxaparvovec for commercial sale had been significantly reduced and included the manufacturing-related costs for the commercial production of valoctocogene roxaparvovec in inventory. A number of factors were taken into consideration based on the information available at the time, including the status in the drug development process, pivotal clinical trial results for the underlying product candidate, results from meetings with the relevant regulatory authorities prior to the filing of regulatory applications, historical experience, as well as potential impediments to the approval process such as product safety or efficacy, as well as commercialization and marketplace trends. If the marketing application is rejected, the manufacturing-related costs for the commercial production of valoctocogene roxaparvovec will be expensed to Research and Development (R&D). In the third quarter of 2020, the Company unexpectedly received a Complete Response Letter from the U.S. Food and Drug Administration (FDA) and a Joint Assessment Report from the European Medicines Agency (EMA) respectively, both indicating that the Company’s regulatory applications for valoctocogene roxaparvovec could not be approved in their present form and requested additional safety and efficacy data from the ongoing Phase 3 study. The Company evaluated the impact of the new requirement for Phase 3 data that is currently unknown and determined the value of the pre-launch inventory was no longer recoverable due to delays in anticipated regulatory approvals. As a result, the Company adjusted the pre-launch inventory to zero, its net realizable value, and recorded $81.2 million to Cost of Sales in the three and nine months ended September 30, 2020. Accounts Payable and Accrued Liabilities consisted of the following: September 30, December 31, Accounts payable and accrued operating expenses $ 218,021 $ 240,981 Accrued compensation expense 137,415 192,467 Accrued rebates payable 65,999 57,163 Accrued royalties payable 20,426 30,797 Lease liabilities 10,930 10,700 Value added taxes payable 7,222 8,395 Forward foreign currency exchange contracts 7,774 10,448 Deferred revenue 3,240 13,037 Other 9,376 6,633 Total accounts payable and accrued liabilities $ 480,403 $ 570,621

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The Company measures certain financial assets and liabilities at fair value in accordance with the policy described in Note 3 – Significant Accounting Policies included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. The following tables present the classification within the fair value hierarchy of financial assets and liabilities not disclosed elsewhere in these Condensed Consolidated Financial Statements that are remeasured on a recurring basis as of September 30, 2020 and December 31, 2019. Other than the Company’s fixed-rate convertible debt disclosed in Note 12 – Debt , there were no financial assets or liabilities that were remeasured using a quoted price in active markets for identical assets (Level 1) as of September 30, 2020 or December 31, 2019. Fair Value Measurements at September 30, 2020 Significant Other Significant Total Assets: Other current assets: NQDC Plan assets $ 1,902 $ — $ 1,902 Other assets: NQDC Plan assets 17,652 — 17,652 Restricted investments (1) 2,987 — 2,987 Total other assets 20,639 — 20,639 Total assets $ 22,541 $ — $ 22,541 Liabilities: Current liabilities: NQDC Plan liability $ 1,902 $ — $ 1,902 Other long-term liabilities: NQDC Plan liability 17,652 — 17,652 Contingent consideration — 54,103 54,103 Total other long-term liabilities 17,652 54,103 71,755 Total liabilities $ 19,554 $ 54,103 $ 73,657 Fair Value Measurements at December 31, 2019 Significant Other Significant Total Assets: Other current assets: NQDC Plan assets $ 1,177 $ — $ 1,177 Other assets: NQDC Plan assets 16,288 — 16,288 Restricted investments (1) 3,168 — 3,168 Total other assets 19,456 — 19,456 Total assets $ 20,633 $ — $ 20,633 Liabilities: Current liabilities: NQDC Plan liability $ 1,177 $ — $ 1,177 Other long-term liabilities: NQDC Plan liability 16,288 — 16,288 Contingent consideration — 50,793 50,793 Total other long-term liabilities 16,288 50,793 67,081 Total liabilities $ 17,465 $ 50,793 $ 68,258 (1) The restricted investments at September 30, 2020 and December 31, 2019 secure the Company's irrevocable standby letters of credit obtained in connection with certain commercial agreements. There were no transfers between levels during the three and nine months ended September 30, 2020. The following table represents a roll forward of contingent consideration. Contingent consideration at December 31, 2019 $ 50,793 Changes in fair value of contingent consideration 1,352 Foreign exchange remeasurement of Euro denominated contingent acquisition consideration 1,958 Contingent consideration at September 30, 2020 $ 54,103

DERIVATIVE INSTRUMENTS AND HEDG

DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES	9 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES	DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES The Company uses forward foreign currency exchange contracts (forward contracts) to hedge certain operational exposures resulting from potential changes in foreign currency exchange rates. Such exposures result from portions of the Company’s forecasted revenues and operating expenses being denominated in currencies other than the U.S. Dollar (USD), primarily the Euro. Certain of these forward contracts are designated as hedging instruments and have maturities up to two and a half years. The Company also enters into forward contracts that are considered to be economic hedges that are not designated as hedging instruments and have maturities up to three months. Whether designated or undesignated, these forward contracts protect against the reduction in value of forecasted foreign currency cash flows resulting from product revenues, royalty revenues, operating expenses and asset or liability positions designated in currencies other than the USD. To receive hedge accounting treatment, cash flow hedges must be highly effective in offsetting changes to expected future cash flows on hedged transactions. The Company does not hold or issue derivative instruments for trading or speculative purposes. The Company is exposed to counterparty credit risk on its derivatives. The Company has established and maintains strict counterparty credit guidelines and enters into hedging agreements with financial institutions that are investment grade or better to minimize the Company’s exposure to potential defaults. The Company is not required to pledge collateral under these agreements. The following table summarizes the aggregate notional amounts for the Company’s derivatives designated as hedging instruments outstanding as of the periods presented. Foreign Exchange Contracts September 30, 2020 December 31, 2019 Sell $ 729,998 $ 820,546 Purchase $ 163,116 $ 212,348 The following table summarizes the aggregate notional amounts for the Company’s derivatives not designated as hedging instruments outstanding as of the periods presented. Foreign Exchange Contracts September 30, 2020 December 31, 2019 Sell $ 41,031 $ 77,335 Purchase $ 30,031 $ 30,818 The fair value carrying amounts of the Company’s derivatives, as classified within the fair value hierarchy, were as follows: Balance Sheet Location September 30, 2020 December 31, 2019 Derivatives designated as hedging instruments: Asset Derivatives - Level 2 (1) Other current assets $ 13,537 $ 19,584 Other assets 4,621 13,539 Subtotal $ 18,158 $ 33,123 Liability Derivatives - Level 2 (1) Accounts payable and accrued liabilities $ 7,704 $ 8,184 Other long-term liabilities 4,406 5,493 Subtotal $ 12,110 $ 13,677 Derivatives not designated as hedging instruments: Asset Derivatives - Level 2 (1) Other current assets $ 16 $ 469 Liability Derivatives - Level 2 (1) Accounts payable and accrued liabilities $ 70 $ 2,264 Total Derivatives Assets $ 18,174 $ 33,592 Total Derivatives Liabilities $ 12,180 $ 15,941 (1) For additional discussion of fair value measurements, see Note 3 – Summary of Significant Accounting Policies included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. The following tables summarize the impact of gains and losses from the Company's derivatives on its Condensed Consolidated Statements of Comprehensive Income (Loss) for the periods presented. Three Months Ended September 30, 2020 September 30, 2019 Derivatives Designated as Cash Flow Hedging Instruments Cash Flow Hedging Gains (Losses) Cash Flow Hedging Gains (Losses) Net product revenues as reported $ 460,741 $ 2,693 $ 450,900 $ 6,196 Operating expenses as reported $ 532,725 $ (815) $ 457,087 $ (1,388) Derivatives Not Designated as Hedging Instruments Gains (Losses) Recognized in Earnings Gains (Losses) Recognized in Earnings Operating expenses $ 4,166 $ (1,286) Nine Months Ended September 30, 2020 September 30, 2019 Derivatives Designated as Cash Flow Hedging Instruments Cash Flow Hedging Gains (Losses) Cash Flow Hedging Gains (Losses) Net product revenues as reported $ 1,368,816 $ 17,301 $ 1,224,458 $ 11,171 Operating expenses as reported $ 1,400,263 $ (4,274) $ 1,340,900 $ (1,885) Derivatives Not Designated as Hedging Instruments Gains (Losses) Recognized in Earnings Gains (Losses) Recognized in Earnings Operating expenses $ 9,600 $ (5,182) As of September 30, 2020, the Company expected to reclassify unrealized gains of $4.8 million from Accumulated Other Comprehensive Income (AOCI) to earnings as the forecasted revenue and operating expense transactions occur over the next 12 months. For additional discussion of balances in AOCI see Note 13 – Accumulated Other Comprehensive Income .

LEASES

LEASES	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Leases	LEASES The following table presents the Company’s right-of-use (ROU) assets and lease liabilities as of September 30, 2020: Lease Classification Classification September 30, December 31, Assets: Operating Other Assets $ 45,764 $ 49,045 Financing Other Assets 12,018 10,389 Total ROU assets $ 57,782 $ 59,434 Liabilities: Current: Operating Accounts payable and accrued liabilities $ 7,813 $ 7,451 Financing Accounts payable and accrued liabilities 3,117 3,249 Noncurrent: Operating Other long-term liabilities 40,831 44,092 Financing Other long-term liabilities 4,570 6,708 Total lease liabilities $ 56,331 $ 61,500 Maturities of lease liabilities as of September 30, 2020 by fiscal year were as follows: Maturity of Lease Liabilities Operating Financing Total Remainder of 2020 $ 3,460 $ 940 $ 4,400 2021 9,908 3,080 12,988 2022 9,095 2,375 11,470 2023 8,055 1,797 9,852 2024 6,253 48 6,301 Thereafter 21,714 20 21,734 Total lease payments 58,485 8,260 66,745 Less: Interest (9,841) (573) (10,414) Present value of lease liabilities $ 48,644 $ 7,687 $ 56,331 Lease costs associated with payments under the Company’s leases were as follows: Three Months Ended Nine Months Ended Lease Cost Classification 2020 2019 2020 2019 Operating (1) Operating Expenses $ 3,227 $ 3,535 $ 8,953 $ 9,946 Financing: Amortization Operating Expenses 841 600 2,307 1,811 Interest expense Operating Expenses 111 142 352 455 Total lease costs $ 4,179 $ 4,277 $ 11,612 $ 12,212 (1) Includes short-term leases and variable lease costs, both of which were not material in the periods presented. The following table includes the weighted average remaining lease terms and the weighted average discount rate used to calculate the present value of the Company’s lease liabilities: Other Information September 30, September 30, Weighted average remaining lease term (in years): Operating leases 7.1 8.0 Financing leases 2.8 4.2 Weighted average discount rate: Operating leases 5.1 % 5.2 % Financing leases 5.2 % 5.4 % As of September 30, 2020, one operating lease is expected to commence in the fourth quarter of 2020. Nine Months Ended September 30, Supplemental Cash Flow Information 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Cash used in operating activities: Operating leases $ 7,007 $ 5,918 Financing leases $ 354 $ 454 Cash used in financing activities: Financing leases $ 6,080 $ 2,027 ROU assets obtained in exchange for lease obligations: Operating leases $ 3,299 $ 9,268 Financing leases $ 3,941 $ 72
Leases	LEASES The following table presents the Company’s right-of-use (ROU) assets and lease liabilities as of September 30, 2020: Lease Classification Classification September 30, December 31, Assets: Operating Other Assets $ 45,764 $ 49,045 Financing Other Assets 12,018 10,389 Total ROU assets $ 57,782 $ 59,434 Liabilities: Current: Operating Accounts payable and accrued liabilities $ 7,813 $ 7,451 Financing Accounts payable and accrued liabilities 3,117 3,249 Noncurrent: Operating Other long-term liabilities 40,831 44,092 Financing Other long-term liabilities 4,570 6,708 Total lease liabilities $ 56,331 $ 61,500 Maturities of lease liabilities as of September 30, 2020 by fiscal year were as follows: Maturity of Lease Liabilities Operating Financing Total Remainder of 2020 $ 3,460 $ 940 $ 4,400 2021 9,908 3,080 12,988 2022 9,095 2,375 11,470 2023 8,055 1,797 9,852 2024 6,253 48 6,301 Thereafter 21,714 20 21,734 Total lease payments 58,485 8,260 66,745 Less: Interest (9,841) (573) (10,414) Present value of lease liabilities $ 48,644 $ 7,687 $ 56,331 Lease costs associated with payments under the Company’s leases were as follows: Three Months Ended Nine Months Ended Lease Cost Classification 2020 2019 2020 2019 Operating (1) Operating Expenses $ 3,227 $ 3,535 $ 8,953 $ 9,946 Financing: Amortization Operating Expenses 841 600 2,307 1,811 Interest expense Operating Expenses 111 142 352 455 Total lease costs $ 4,179 $ 4,277 $ 11,612 $ 12,212 (1) Includes short-term leases and variable lease costs, both of which were not material in the periods presented. The following table includes the weighted average remaining lease terms and the weighted average discount rate used to calculate the present value of the Company’s lease liabilities: Other Information September 30, September 30, Weighted average remaining lease term (in years): Operating leases 7.1 8.0 Financing leases 2.8 4.2 Weighted average discount rate: Operating leases 5.1 % 5.2 % Financing leases 5.2 % 5.4 % As of September 30, 2020, one operating lease is expected to commence in the fourth quarter of 2020. Nine Months Ended September 30, Supplemental Cash Flow Information 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Cash used in operating activities: Operating leases $ 7,007 $ 5,918 Financing leases $ 354 $ 454 Cash used in financing activities: Financing leases $ 6,080 $ 2,027 ROU assets obtained in exchange for lease obligations: Operating leases $ 3,299 $ 9,268 Financing leases $ 3,941 $ 72

DEBT

DEBT	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
DEBT	DEBT Convertible Notes As of September 30, 2020, the Company had outstanding fixed-rate notes with varying maturities for an undiscounted aggregate principal amount of $1.5 billion (collectively the Notes). The Notes are senior subordinated convertible obligations, and interest is payable in arrears, semi-annually. The following table summarizes information regarding the Company’s convertible debt: September 30, December 31, 1.25% senior subordinated convertible notes due in May 2027 (the 2027 Notes) $ 600,000 $ — Unamortized discount (12,792) — Unamortized deferred offering costs (709) — 2027 Notes, net 586,499 — 0.599% senior subordinated convertible notes due in August 2024 (the 2024 Notes) 495,000 495,000 Unamortized discount (5,470) (6,533) Unamortized deferred offering costs (1,865) (2,229) 2024 Notes, net 487,665 486,238 1.50% senior subordinated convertible notes due in October 2020 (the 2020 Notes) 374,993 374,993 Unamortized discount (649) (12,078) Unamortized deferred offering costs (54) (1,033) 2020 Notes, net (1) 374,290 361,882 Total convertible debt, net $ 1,448,454 $ 848,120 Fair value of fixed rate convertible debt (2) : 2027 Notes $ 590,010 $ — 2024 Notes 517,730 521,839 2020 Notes 374,997 405,679 Total fair value of fixed rate convertible debt $ 1,482,737 $ 927,518 (1) The 2020 Notes are classified as a current liability in the periods presented because they matured on October 15, 2020 and were settled in cash for approximately $375.0 million. No shares were issued in connection with the settlement as the Company’s share price did not exceed the conversion price of $94.15, as measured over a 25-day averaging period, and the capped call transaction entered into concurrently with the issuance of notes was not triggered. The Company incurred no gain or loss upon the extinguishment of the 2020 Notes. (2) The fair value of the Company’s fixed-rate convertible debt is based on open market trades and is classified as Level 1 in the fair value hierarchy. For additional discussion of fair value measurements, see Note 3 – Summary of Significant Accounting Policies included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Interest expense on the Company’s convertible debt consisted of the following: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Accretion of discount on convertible notes $ 4,696 $ 4,005 $ 13,201 $ 11,860 Coupon interest expense 4,255 2,271 9,443 6,681 Amortization of debt issuance costs 535 508 1,565 1,522 Total interest expense on convertible debt $ 9,486 $ 6,784 $ 24,209 $ 20,063 2027 Notes In May 2020, the Company issued $600.0 million in aggregate principal amount of senior subordinated unsecured convertible notes with a maturity date of May 15, 2027. The 2027 Notes were issued to the public at par value and bear interest at the rate of 1.25% per annum. Interest is payable semi-annually in cash in arrears on May 15 and November 15 of each year, beginning November 15, 2020. The 2027 Notes are convertible, at the option of the holder into shares of the Company’s common stock. The initial conversion rate for the 2027 Notes is 7.2743 shares per $1,000 principal amount of the 2027 Notes, which represents a conversion price of approximately $137.47 per share, subject to adjustment under certain conditions. Following certain corporate transactions, the Company will, in certain circumstances, increase the conversion rate for a holder that elects to convert its 2027 Notes in connection with such corporate transactions by a number of additional shares of the Company’s common stock. A holder may convert fewer than all of such holder’s 2027 Notes so long as the amount of the 2027 Notes converted is an integral multiple of $1,000 principal amount. Net proceeds from the offering were $585.8 million. In connection with the issuance of the 2027 Notes, the Company recorded a discount on the 2027 Notes of $13.5 million, which will be accreted and recorded as additional interest expense over the life of the 2027 Notes. The Company also incurred $0.7 million of issuance costs, which were deferred and are being amortized over the life of the 2027 Notes and recorded as additional interest expense. The 2027 Notes are senior subordinated, unsecured obligations, and rank (i) subordinated in right of payment to the prior payment in full of all of the Company’s existing and future senior debt, (ii) equal in right of payment with the Company’s existing and future senior subordinated debt, (iii) senior in right of payment to the Company’s existing and future indebtedness that is expressly subordinated in right of payment to the notes, (vi) effectively subordinated to the Company’s existing and future secured indebtedness, to the extent of the value of the collateral securing that indebtedness, and (v) structurally subordinated to all existing and future indebtedness and other liabilities, including trade payables, and (to the extent the Company is not a holder thereof) preferred equity, if any, of the Company’s subsidiaries. Upon the occurrence of a “fundamental change,” as defined in the indenture governing the 2027 Notes, the holders may require the Company to repurchase all or a portion of such holder’s 2027 Notes for cash at 100% of the principal amount of the 2027 Notes being purchased, plus any accrued and unpaid interest. The offer and sale of the 2027 Notes and the shares of the Company’s common stock issuable upon conversion of the 2027 Notes have not been registered under the Securities Act or any state securities laws and the 2027 Notes were offered only to qualified institutional buyers as defined in Rule 144A under the Securities Act. See Note 13 - Debt in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 for additional information related to the Company’s convertible debt. Revolving Credit Facility In October 2018, the Company entered into an unsecured revolving credit facility of up to $200.0 million (the 2018 Credit Facility). The 2018 Credit Facility includes a letter of credit subfacility and a swingline loan subfacility and is intended to finance ongoing working capital needs and for other general corporate purposes. Borrowings under the 2018 Credit Facility bear interest, at the Company’s option, at a rate equal to either (a) the LIBOR rate (except that if LIBOR is less than zero it shall be deemed to be zero for purposes of the 2018 Credit Facility), or LIBOR successor rate, plus an applicable margin ranging from 1.00% to 1.95% per annum, based upon the Company’s net leverage ratio and earnings before interest, taxes, depreciation and amortization (EBITDA) for each of the two most recently ended four-quarter measurement periods, or (b) the Base Rate, generally the prime lending rate, plus an applicable margin ranging from 0.00% to 0.95%, based upon the Company’s net leverage ratio and EBITDA for each of the two most recently ended four-quarter measurement periods. Commitment fees payable on the undrawn amount

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME	ACCUMULATED OTHER COMPREHENSIVE INCOME The following table summarizes amounts reclassified out of AOCI and their effect on the Company’s Condensed Consolidated Statements of Comprehensive Income (Loss) for the three and nine months ended September 30, 2020 and 2019. Condensed Consolidated Three Months Ended Nine Months Ended 2020 2019 2020 2019 Gains (losses) on cash flow hedges: Forward contracts Net product revenues $ 2,693 $ 6,196 $ 17,301 $ 11,171 Forward contracts Operating expenses (815) (1,388) (4,274) (1,885) Total gain (loss) on cash flow hedges $ 1,878 $ 4,808 $ 13,027 $ 9,286 The following tables summarize changes in the accumulated balances for each component of AOCI, including current period other comprehensive income (loss) and reclassifications out of AOCI for the three and nine months ended September 30, 2020 and 2019. Three Months Ended September 30, 2020 Unrealized Gains Unrealized Gains Other Total AOCI balance at June 30, 2020 $ 22,963 $ 7,087 $ — $ 30,050 Other comprehensive income (loss) before reclassifications (16,094) (2,201) — (18,295) Less: net gain (loss) reclassified from AOCI 1,878 — — 1,878 Tax effect — 508 — 508 Net current-period other comprehensive income (loss) (17,972) (1,693) — (19,665) AOCI balance at September 30, 2020 $ 4,991 $ 5,394 $ — $ 10,385 Three Months Ended September 30, 2019 Unrealized Gains Unrealized Gains Other Total AOCI balance at June 30, 2019 $ 14,181 $ 3,271 $ (13) $ 17,439 Other comprehensive income (loss) before 23,973 522 (3) 24,492 Less: gain (loss) reclassified from AOCI 4,808 — — 4,808 Tax effect — (120) — (120) Net current-period other comprehensive income (loss) 19,165 402 (3) 19,564 AOCI balance at September 30, 2019 $ 33,346 $ 3,673 $ (16) $ 37,003 Nine Months Ended September 30, 2020 Unrealized Gains Unrealized Gains Other Total AOCI balance at December 31, 2019 $ 16,614 $ 3,565 $ (15) $ 20,164 Other comprehensive income (loss) before 1,404 2,379 15 3,798 Less: gain (loss) reclassified from AOCI 13,027 — 13,027 Tax effect — (550) — (550) Net current-period other comprehensive income (loss) (11,623) 1,829 15 (9,779) AOCI balance at September 30, 2020 $ 4,991 $ 5,394 $ — $ 10,385 Nine Months Ended September 30, 2019 Unrealized Gains Unrealized Gains Other Total AOCI balance at December 31, 2018 $ 7,201 $ (1,917) $ (13) $ 5,271 Other comprehensive income (loss) before 35,431 7,256 (3) 42,684 Less: gain (loss) reclassified from AOCI 9,286 — — 9,286 Tax effect — (1,666) — (1,666) Net current-period other comprehensive income (loss) 26,145 5,590 (3) 31,732 AOCI balance at September 30, 2019 $ 33,346 $ 3,673 $ (16) $ 37,003

REVENUE, CREDIT CONCENTRATIONS

REVENUE, CREDIT CONCENTRATIONS AND GEOGRAPHIC INFORMATION	9 Months Ended
	Sep. 30, 2020
Concentration Risk And Geographic Information [Abstract]
REVENUE, CREDIT CONCENTRATIONS AND GEOGRAPHIC INFORMATION	REVENUE, CREDIT CONCENTRATIONS AND GEOGRAPHIC INFORMATIONThe Company operates in one business segment, which primarily focuses on the development and commercialization of innovative therapies for people with serious and life-threatening rare diseases and medical conditions. The Company considers there to be revenue concentration risks for regions where Net Product Revenues exceed 10% of consolidated Net Product Revenues. The concentration of the Company’s Net Product Revenues within the regions below may have a material adverse effect on the Company’s revenues and results of operations if sales in the respective regions experience difficulties. The following table disaggregates Total Revenues from external customers and collaborative partners by geographic region. Net product revenues by geographic region are based on patient location for the Company’s commercial products, except for Aldurazyme, which is sold exclusively to Sanofi Genzyme (Genzyme) who markets and sells Aldurazyme world-wide. Aldurazyme revenues earned by the Company are included in the U.S. region as the transactions are with Genzyme, whose headquarters is located in the U.S. Three Months Ended Nine Months Ended 2020 2019 2020 2019 Total revenues by geographic region: United States $ 252,948 $ 201,874 $ 729,672 $ 562,217 Europe 121,158 125,485 375,453 369,585 Latin America 44,064 83,799 141,852 164,132 Rest of world 58,614 49,939 161,361 153,671 Total revenues $ 476,784 $ 461,097 $ 1,408,338 $ 1,249,605 The following table disaggregates Net Product Revenues by product. Three Months Ended Nine Months Ended 2020 2019 2020 2019 Net product revenues by product: Vimizim $ 147,891 $ 163,466 $ 401,789 $ 411,953 Kuvan 123,993 120,524 368,604 340,771 Naglazyme 76,323 94,408 271,585 279,462 Palynziq 46,092 24,142 121,354 55,250 Brineura 25,455 19,840 75,223 46,815 Firdapse — 5,668 1,316 16,262 Total net product revenues marketed by the Company $ 419,754 $ 428,048 $ 1,239,871 $ 1,150,513 Aldurazyme net product revenues marketed by Genzyme 40,987 22,852 $ 128,945 $ 73,945 Total net product revenues $ 460,741 $ 450,900 $ 1,368,816 $ 1,224,458 The table below disaggregates total Net Product Revenues based on patient location for products sold directly by the Company, and global sales of Aldurazyme, which is marketed by Genzyme. Three Months Ended Nine Months Ended 2020 2019 2020 2019 United States $ 203,892 $ 175,127 $ 582,734 $ 480,330 Europe 115,548 121,363 360,718 358,041 Latin America 44,064 83,799 141,852 164,132 Rest of world 56,250 47,759 154,567 148,010 Total net product revenues marketed by the Company 419,754 428,048 1,239,871 1,150,513 Aldurazyme net product revenues marketed by Genzyme 40,987 22,852 128,945 73,945 Total net product revenues $ 460,741 $ 450,900 $ 1,368,816 $ 1,224,458 The following table illustrates the percentage of the Company’s total Net Product Revenues attributed to the Company’s largest customers for the periods presented. Three Months Ended Nine Months Ended 2020 2019 2020 2019 Customer A 16 % 16 % 15 % 17 % Customer B 14 % 13 % 14 % 12 % Customer C 11 % 10 % 12 % 11 % Customer D 1 % 12 % 3 % 6 % Total 42 % 51 % 44 % 46 % On a consolidated basis, two customers accounted for 33% and 15% of the September 30, 2020 accounts receivable balance, respectively, compared to December 31, 2019, when two customers accounted for 24% and 16% of the accounts receivable balance, respectively. As of September 30, 2020, and December 31, 2019, the accounts receivable balance for Genzyme included $106.5 million and $60.2 million, respectively, of unbilled accounts receivable, which becomes payable to the Company when the product is sold by Genzyme. The Company does not require collateral from its customers but does perform periodic credit evaluations of its customers’ financial condition and requires prepayments in certain circumstances. The outbreak of COVID-19 continues to affect economies and business around the world. The Company experienced a modest impact on its global revenue sources, mostly in the form of demand interruptions such as missed patient infusions and delayed treatment starts for new patients, in the three and nine months ended September 30, 2020 and the Company anticipates a continued impact on its financial results for the remainder of 2020 and into fiscal year 2021. The extent and duration of such effects are highly uncertain and difficult to predict. The Company is actively monitoring and managing its response and assessing actual and potential impacts to its operating results and financial condition, as well as developments in its business, which could further impact developments, trends and expectations. See the risk factor related to the impact of the coronavirus pandemic, “The coronavirus, or COVID-19, pandemic could materially adversely affect our business, results of operations and financial condition.” described in “Risk Factors” in Part II, Item 1A of this Quarterly Report, for additional details on the impact of the COVID-19 pandemic. The Company is mindful that conditions in the current macroeconomic environment could affect the Company’s ability to achieve its goals. The Company sells its products in countries that face economic volatility and weakness. Although the Company has historically collected receivables from customers in certain countries, sustained weakness or further deterioration of the local economies and currencies and effects of the impact of the ongoing COVID-19 pandemic may cause customers in those countries to delay payment or be unable to pay for the Company’s products. The Company believes that the allowances for doubtful accounts related to these countries, if any, are adequate based on its analysis of the specific business circumstances and expectations of collection for each of the underlying accounts in these countries. The Company will continue to monitor these conditions and will attempt to adjust its business processes, as appropriate, to mitigate macroeconomic risks to its business.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION The Company has stockholder-approved equity incentive plans that provide for the granting of service-based restricted stock units (RSUs), market-based RSUs, performance-based RSUs, stock options and other types of awards to its employees, officers and non-employee directors. Compensation expense included in the Company’s Condensed Consolidated Statements of Comprehensive Income (Loss) for all stock-based compensation arrangements was as follows: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Cost of sales $ 10,342 $ 4,093 $ 20,381 $ 12,629 Research and development 15,705 14,261 45,333 43,037 Selling, general and administrative 24,122 20,819 76,411 66,097 Total stock-based compensation expense $ 50,169 $ 39,173 $ 142,125 $ 121,763 Stock-based compensation of $4.9 million and $14.9 million was capitalized into inventory for the three and nine months ended September 30, 2020, respectively. Stock-based compensation of $5.1 million and $13.2 million was capitalized into inventory for the three and nine months ended September 30, 2019, respectively. Capitalized stock-based compensation is recognized as cost of sales when the related product is sold. Restricted Stock Unit Awards with Market Conditions In March 2020, the Compensation Committee and Board approved the grant of 126,710 RSUs with market-based vesting conditions (base TSR-RSUs) to certain executives. These base TSR-RSUs vest, if at all, in full following a three-year service period only if certain total shareholder return (TSR) results relative to the Nasdaq Biotechnology Index comparative companies are achieved. The number of shares that may be earned range between 0% and 200% of the base TSR-RSUs, with a ceiling achievement level of 100% of the base TSR-RSUs in the event the Company’s absolute TSR multiplier is above the 50th percentile but the Company’s TSR multiplier is negative on an absolute basis. The Company utilized a Monte Carlo simulation model to determine the grant date fair value of $112.12 per base TSR-RSU. Compensation expense for awards with market conditions is recognized over the service period using the straight-line method and is not reversed if the market condition is not met. Restricted Stock Unit Awards with Performance Conditions In March 2020, the Compensation Committee and Board approved the grant of 63,400 RSUs with performance-based vesting conditions (base RSUs) and a grant date fair value of $73.82 per RSU. This award is contingent upon the achievement of a three-year Non-GAAP income target and the awarded RSUs, if any, vest ratably over a three-year service period. The Company evaluated the target in the context of its current long-range financial plan and determined that attainment of the target was probable for accounting purposes commencing in the first quarter of 2020. The number of shares that may be earned range between 50% and 200% of the base RSUs. In March 2020, the Compensation Committee and Board approved the grant of 63,400 RSUs with performance-based vesting conditions (base RSUs) and a grant date fair value of $73.82 per RSU. This award is contingent upon the achievement of a three-year strategic goal target and the awarded RSUs, if any, vest ratably over a three-year service period. The Company evaluated the target in the context of its product candidate development pipeline and planned regulatory activity and determined that attainment of the target was probable for accounting purposes commencing in the first quarter of 2020. The number of shares that may be earned range between 50% and 200% of the base RSUs.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXESIn the third quarter of 2020, the Company completed an intra-entity transfer of certain intellectual property rights to an Irish subsidiary where the Company’s Ex-US regional headquarters are located and has significant manufacturing and commercial operations, to better align ownership of intellectual property rights with how the business operates. The transaction did not result in a taxable gain; however, the Company’s Irish subsidiary recognized a deferred tax asset for the book and tax basis difference of the transferred intellectual property rights. As a result, the Company recognized a deferred tax asset of $835.1 million and related tax benefit on its Condensed Consolidated Financial Statements based on the fair value of the transferred intellectual property rights. The tax deductions related to the amortization of these intangible assets will be recognized in the future and any amortization not deducted for tax purposes will be carried forward indefinitely under Irish tax laws. The Company expects to be able to realize the deferred tax asset resulting from this transaction and has not recorded a valuation allowance as of September 30, 2020.

NET INCOME (LOSS) PER COMMON SH

NET INCOME (LOSS) PER COMMON SHARE	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
NET INCOME (LOSS) PER COMMON SHARE	NET INCOME (LOSS) PER COMMON SHARE Potentially issuable shares of common stock include shares issuable upon the exercise of outstanding employee stock option awards, common stock issuable under the Company’s Employee Share Purchase Plan (ESPP), unvested RSUs, common stock held by the NQDC and contingent issuances of common stock related to the Company’s convertible debt. The following table sets forth the computation of basic and diluted earnings per common share (common shares in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Numerator: Net Income (Loss), basic $ 784,803 $ 55,036 $ 837,001 $ (38,872) Add: Interest on convertible notes 7,070 937 18,333 — Net Income (Loss), diluted $ 791,873 $ 55,973 $ 855,334 $ (38,872) Denominator: Weighted-average common shares outstanding, basic 181,142 179,289 180,592 178,873 Effect of dilutive securities: Options to purchase common stock 1,731 1,560 1,728 — Common stock issuable under the 2020 notes 3,983 — 3,983 — Common stock issuable under the 2024 notes 3,970 3,970 3,970 — Common stock issuable under the 2027 notes 4,365 — 2,373 — Unvested RSUs 1,926 669 1,765 — Common stock potentially issuable for ESPP purchases 346 231 337 — Common shares held by the NQDC 211 205 211 — Weighted-average common shares outstanding, diluted 197,674 185,924 194,959 178,873 Net Income (Loss) per common share, basic $ 4.33 $ 0.31 4.63 (0.22) Net Income (Loss) per common share, diluted $ 4.01 $ 0.30 4.39 (0.22) In addition to the equity instruments included in the table above, the table below presents potential shares of common stock that were excluded from the computation of diluted earnings per common share as they were anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Options to purchase common stock 5,172 5,829 5,175 7,388 Common stock issuable under the 2020 Notes — 3,983 — 3,983 Common stock issuable under the 2024 Notes — — — 3,970 Unvested RSUs 2,900 3,360 3,060 4,029 Common stock potentially issuable for ESPP purchases 193 222 204 453 Common stock held by the NQDC — — — 205 Total number of potentially issuable shares 8,265 13,394 8,439 20,028 The potential effect of the capped call transactions and potential shares issuable under the 2020 Notes were excluded from the calculation of diluted net income (loss) per share in the three and nine months ended September 30, 2020 and 2019, as the Company’s closing price on September 30, 2020 and 2019 did not exceed the conversion price of $94.15 per share. The Company’s 2020 Notes matured on October 15, 2020 and were settled in cash. T he potential effect of the capped call transactions with respect to the 2020 Notes was excluded from the diluted net income (loss) per share as of September 30, 2020. There is no similar capped call transaction associated with the 2024 Notes or the 2027 Notes. See Note 12 – Debt for additional information on the Company’s 2020 Notes and 2027 Notes. Refer to Note 13 - Debt to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 for additional information related to the 2024 Notes and details of the capped call transaction.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Contingencies From time to time the Company is involved in legal actions arising in the normal course of its business. The process of resolving matters through litigation or other means is inherently uncertain and it is possible that an unfavorable resolution of these matters could adversely affect the Company, its results of operations, financial condition or cash flows. The Company’s general practice is to expense legal fees as services are rendered in connection with legal matters, and to accrue for liabilities when losses are probable and reasonably estimable. Contingent Payments As of September 30, 2020, the Company was subject to contingent payments totaling approximately $622.4 million upon achievement of certain development, regulatory and commercial sales milestones, if they occur before certain dates in the future. Of this amount, $235.0 million related to an early stage development programs licensed from a third party in the second quarter of 2020, $70.3 million related to the acquisition of certain rights and other assets with respect to Kuvan and Palynziq from a third party and $236.0 million related to programs that are no longer being developed. As of September 30, 2020, the Company recorded a total of $54.1 million of contingent liabilities on its Condensed Consolidated Balances Sheet. See Note 9 – Fair Value Measurements to these Condensed Consolidated Financial Statements for further information regarding the fair value of the Company’s contingent consideration. Other Commitments In the normal course of business, the Company enters into various firm purchase commitments primarily related to active pharmaceutical ingredients, certain inventory-related items and certain third-party R&D services. As of September 30, 2020, such commitments and other minimum contractual obligations for clinical and post-marketing services were estimated at approximately $150.3 million.

BASIS OF PRESENTATION (Policies

BASIS OF PRESENTATION (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	The accompanying Condensed Consolidated Financial Statements have been prepared pursuant to United States (U.S.) generally accepted accounting principles (U.S. GAAP) and the rules and regulations of the SEC for Quarterly Reports on Form 10-Q and do not include all of the information and note disclosures required by U.S. GAAP for complete financial statements, although the Company believes that the disclosures herein are adequate to ensure that the information presented is not misleading. The Condensed Consolidated Financial Statements should therefore be read in conjunction with the Consolidated Financial Statements and Notes thereto for the fiscal year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2020 or any other period. U.S. GAAP requires management to make estimates and assumptions that affect amounts reported in the Condensed Consolidated Financial Statements and accompanying disclosures. Although these estimates are based on management’s best knowledge of current events and actions that the Company may undertake in the future, actual results may be different from those estimates. The Condensed Consolidated Financial Statements reflect all adjustments of a normal, recurring nature that are, in the opinion of management, necessary for a fair presentation of results for these interim periods. The full extent to which the novel coronavirus disease (referred to as COVID-19) pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including revenues, expenses, reserves and allowances, manufacturing, clinical trials and research and development costs, will depend on future developments that are highly uncertain at this time. As events continue to evolve and additional information becomes available, the Company’s estimates may change materially in future periods. Management performed an evaluation of the Company’s activities through the date of filing of this Quarterly Report on Form 10-Q, and has concluded that, except for the maturity and settlement of our convertible debt discussed in Note 12 - Debt , there were no subsequent events or transactions that occurred subsequent to the balance sheet date prior to filing this Quarterly Report on Form 10-Q that would require recognition or disclosure in the Condensed Consolidated Financial Statements.
New Accounting Pronouncements	On January 1, 2020, the Company adopted Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13), as amended, using a modified retrospective approach. The standard has amended the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the incurred-loss model with an expected-loss model. This new standard also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income rather than by reducing the carrying amount under the current, other-than-temporary impairment model. Results for reporting periods beginning January 1, 2020 are presented under ASU 2016-13 and the adoption of this standard had no impact on the Company’s Financial Statements.

FINANCIAL INSTRUMENTS (Tables)

FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Cash, Cash Equivalents and Available-for-Sale Securities by Significant Investment Category	The following tables show the Company’s cash, cash equivalents and available-for-sale securities by significant investment category for each period presented: September 30, 2020 Amortized Cost Gross Gross Aggregate Fair Value Cash and Cash Equivalents Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash $ 378,705 $ — $ — $ 378,705 $ 378,705 $ — $ — Level 2: Money market instruments 557,006 — — 557,006 557,006 — — Corporate debt securities 435,954 4,558 (14) 440,498 — 280,000 160,498 U.S. government agency securities 361,336 2,182 (1) 363,517 79,964 199,559 83,994 Asset-backed securities 23,430 129 — 23,559 — 3,639 19,920 Commercial paper 6,800 — — 6,800 — 6,800 — Foreign and other 549 161 — 710 — — 710 Subtotal 1,385,075 7,030 (15) 1,392,090 636,970 489,998 265,122 Total $ 1,763,780 $ 7,030 $ (15) $ 1,770,795 $ 1,015,675 $ 489,998 $ 265,122 December 31, 2019 Amortized Cost Gross Gross Aggregate Fair Value Cash and Cash Equivalents Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash $ 259,347 $ — $ — $ 259,347 $ 259,347 $ — $ — Level 2: Money market instruments 173,100 — — 173,100 173,100 — — Corporate debt securities 518,523 3,575 (12) 522,086 — 233,294 288,792 U.S. government agency securities 209,633 993 (67) 210,559 4,999 83,067 122,493 Foreign and other 549 145 (1) 693 — — 693 Subtotal 901,805 4,713 (80) 906,438 178,099 316,361 411,978 Total $ 1,161,152 $ 4,713 $ (80) $ 1,165,785 $ 437,446 $ 316,361 $ 411,978 (1) The Company’s short-term marketable securities mature in one year or less. one

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	9 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Intangible assets consisted of the following: September 30, December 31, Intangible assets: Finite-lived intangible assets $ 638,468 $ 652,734 Accumulated amortization (211,296) (196,154) Net carrying value $ 427,172 $ 456,580

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Schedule of Property Plant and Equipment Net	Property, plant and equipment, net consisted of the following: September 30, December 31, Building and improvements $ 756,479 $ 725,906 Manufacturing and laboratory equipment 402,357 366,951 Computer hardware and software 187,722 167,554 Land 90,418 90,418 Leasehold improvements 52,479 51,324 Furniture and equipment 39,360 38,569 Land improvements 7,349 7,349 Construction-in-progress 92,581 111,897 1,628,745 1,559,968 Accumulated depreciation (613,683) (549,100) Total property, plant and equipment, net $ 1,015,062 $ 1,010,868 Three Months Ended Nine Months Ended 2020 2019 2020 2019 Depreciation expense $ 22,187 $ 24,238 $ 65,749 $ 67,206 Depreciation capitalized into inventory $ 10,883 $ 9,807 $ 34,053 $ 24,894

SUPPLEMENTAL BALANCE SHEET IN_2

SUPPLEMENTAL BALANCE SHEET INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Inventory	Inventory consisted of the following: September 30, December 31, Raw materials $ 73,857 $ 74,442 Work-in-process 296,685 349,978 Finished goods 330,305 255,855 Total inventory $ 700,847 $ 680,275
Schedule of Accounts Payable and Accrued Liabilities	Accounts Payable and Accrued Liabilities consisted of the following: September 30, December 31, Accounts payable and accrued operating expenses $ 218,021 $ 240,981 Accrued compensation expense 137,415 192,467 Accrued rebates payable 65,999 57,163 Accrued royalties payable 20,426 30,797 Lease liabilities 10,930 10,700 Value added taxes payable 7,222 8,395 Forward foreign currency exchange contracts 7,774 10,448 Deferred revenue 3,240 13,037 Other 9,376 6,633 Total accounts payable and accrued liabilities $ 480,403 $ 570,621

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	The following tables present the classification within the fair value hierarchy of financial assets and liabilities not disclosed elsewhere in these Condensed Consolidated Financial Statements that are remeasured on a recurring basis as of September 30, 2020 and December 31, 2019. Other than the Company’s fixed-rate convertible debt disclosed in Note 12 – Debt , there were no financial assets or liabilities that were remeasured using a quoted price in active markets for identical assets (Level 1) as of September 30, 2020 or December 31, 2019. Fair Value Measurements at September 30, 2020 Significant Other Significant Total Assets: Other current assets: NQDC Plan assets $ 1,902 $ — $ 1,902 Other assets: NQDC Plan assets 17,652 — 17,652 Restricted investments (1) 2,987 — 2,987 Total other assets 20,639 — 20,639 Total assets $ 22,541 $ — $ 22,541 Liabilities: Current liabilities: NQDC Plan liability $ 1,902 $ — $ 1,902 Other long-term liabilities: NQDC Plan liability 17,652 — 17,652 Contingent consideration — 54,103 54,103 Total other long-term liabilities 17,652 54,103 71,755 Total liabilities $ 19,554 $ 54,103 $ 73,657 Fair Value Measurements at December 31, 2019 Significant Other Significant Total Assets: Other current assets: NQDC Plan assets $ 1,177 $ — $ 1,177 Other assets: NQDC Plan assets 16,288 — 16,288 Restricted investments (1) 3,168 — 3,168 Total other assets 19,456 — 19,456 Total assets $ 20,633 $ — $ 20,633 Liabilities: Current liabilities: NQDC Plan liability $ 1,177 $ — $ 1,177 Other long-term liabilities: NQDC Plan liability 16,288 — 16,288 Contingent consideration — 50,793 50,793 Total other long-term liabilities 16,288 50,793 67,081 Total liabilities $ 17,465 $ 50,793 $ 68,258 (1) The restricted investments at September 30, 2020 and December 31, 2019 secure the Company's irrevocable standby letters of credit obtained in connection with certain commercial agreements.
Liabilities Measured at Fair Value on Recurring Basis Using Level 3 Inputs	The following table represents a roll forward of contingent consideration. Contingent consideration at December 31, 2019 $ 50,793 Changes in fair value of contingent consideration 1,352 Foreign exchange remeasurement of Euro denominated contingent acquisition consideration 1,958 Contingent consideration at September 30, 2020 $ 54,103

DERIVATIVE INSTRUMENTS AND HE_2

DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES (Tables)	9 Months Ended
	Sep. 30, 2020
Derivative [Line Items]
Fair Value Carrying Amount of Derivatives	The fair value carrying amounts of the Company’s derivatives, as classified within the fair value hierarchy, were as follows: Balance Sheet Location September 30, 2020 December 31, 2019 Derivatives designated as hedging instruments: Asset Derivatives - Level 2 (1) Other current assets $ 13,537 $ 19,584 Other assets 4,621 13,539 Subtotal $ 18,158 $ 33,123 Liability Derivatives - Level 2 (1) Accounts payable and accrued liabilities $ 7,704 $ 8,184 Other long-term liabilities 4,406 5,493 Subtotal $ 12,110 $ 13,677 Derivatives not designated as hedging instruments: Asset Derivatives - Level 2 (1) Other current assets $ 16 $ 469 Liability Derivatives - Level 2 (1) Accounts payable and accrued liabilities $ 70 $ 2,264 Total Derivatives Assets $ 18,174 $ 33,592 Total Derivatives Liabilities $ 12,180 $ 15,941 (1) For additional discussion of fair value measurements, see Note 3 – Summary of Significant Accounting Policies included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019.
Summary of Impact of Gains and Losses from Derivatives Designated as Hedging Instruments	The following tables summarize the impact of gains and losses from the Company's derivatives on its Condensed Consolidated Statements of Comprehensive Income (Loss) for the periods presented. Three Months Ended September 30, 2020 September 30, 2019 Derivatives Designated as Cash Flow Hedging Instruments Cash Flow Hedging Gains (Losses) Cash Flow Hedging Gains (Losses) Net product revenues as reported $ 460,741 $ 2,693 $ 450,900 $ 6,196 Operating expenses as reported $ 532,725 $ (815) $ 457,087 $ (1,388) Derivatives Not Designated as Hedging Instruments Gains (Losses) Recognized in Earnings Gains (Losses) Recognized in Earnings Operating expenses $ 4,166 $ (1,286) Nine Months Ended September 30, 2020 September 30, 2019 Derivatives Designated as Cash Flow Hedging Instruments Cash Flow Hedging Gains (Losses) Cash Flow Hedging Gains (Losses) Net product revenues as reported $ 1,368,816 $ 17,301 $ 1,224,458 $ 11,171 Operating expenses as reported $ 1,400,263 $ (4,274) $ 1,340,900 $ (1,885) Derivatives Not Designated as Hedging Instruments Gains (Losses) Recognized in Earnings Gains (Losses) Recognized in Earnings Operating expenses $ 9,600 $ (5,182)
Derivatives Designated As Hedging Instruments
Derivative [Line Items]
Summary of Derivatives Designated as Hedging Instruments Outstanding	The following table summarizes the aggregate notional amounts for the Company’s derivatives designated as hedging instruments outstanding as of the periods presented. Foreign Exchange Contracts September 30, 2020 December 31, 2019 Sell $ 729,998 $ 820,546 Purchase $ 163,116 $ 212,348
Not Designated as Hedging Instrument
Derivative [Line Items]
Summary of Derivatives Designated as Hedging Instruments Outstanding	The following table summarizes the aggregate notional amounts for the Company’s derivatives not designated as hedging instruments outstanding as of the periods presented. Foreign Exchange Contracts September 30, 2020 December 31, 2019 Sell $ 41,031 $ 77,335 Purchase $ 30,031 $ 30,818

LEASES (Tables)

LEASES (Tables)	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Schedule of ROU Assets and Lease Liabilities	The following table presents the Company’s right-of-use (ROU) assets and lease liabilities as of September 30, 2020: Lease Classification Classification September 30, December 31, Assets: Operating Other Assets $ 45,764 $ 49,045 Financing Other Assets 12,018 10,389 Total ROU assets $ 57,782 $ 59,434 Liabilities: Current: Operating Accounts payable and accrued liabilities $ 7,813 $ 7,451 Financing Accounts payable and accrued liabilities 3,117 3,249 Noncurrent: Operating Other long-term liabilities 40,831 44,092 Financing Other long-term liabilities 4,570 6,708 Total lease liabilities $ 56,331 $ 61,500
Schedule of Maturities of Operating Lease Liabilities	Maturities of lease liabilities as of September 30, 2020 by fiscal year were as follows: Maturity of Lease Liabilities Operating Financing Total Remainder of 2020 $ 3,460 $ 940 $ 4,400 2021 9,908 3,080 12,988 2022 9,095 2,375 11,470 2023 8,055 1,797 9,852 2024 6,253 48 6,301 Thereafter 21,714 20 21,734 Total lease payments 58,485 8,260 66,745 Less: Interest (9,841) (573) (10,414) Present value of lease liabilities $ 48,644 $ 7,687 $ 56,331
Schedule of Maturities of Finance Lease Liabilities	Maturities of lease liabilities as of September 30, 2020 by fiscal year were as follows: Maturity of Lease Liabilities Operating Financing Total Remainder of 2020 $ 3,460 $ 940 $ 4,400 2021 9,908 3,080 12,988 2022 9,095 2,375 11,470 2023 8,055 1,797 9,852 2024 6,253 48 6,301 Thereafter 21,714 20 21,734 Total lease payments 58,485 8,260 66,745 Less: Interest (9,841) (573) (10,414) Present value of lease liabilities $ 48,644 $ 7,687 $ 56,331
Schedule of Lease Cost	Lease costs associated with payments under the Company’s leases were as follows: Three Months Ended Nine Months Ended Lease Cost Classification 2020 2019 2020 2019 Operating (1) Operating Expenses $ 3,227 $ 3,535 $ 8,953 $ 9,946 Financing: Amortization Operating Expenses 841 600 2,307 1,811 Interest expense Operating Expenses 111 142 352 455 Total lease costs $ 4,179 $ 4,277 $ 11,612 $ 12,212 (1) Includes short-term leases and variable lease costs, both of which were not material in the periods presented. Nine Months Ended September 30, Supplemental Cash Flow Information 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Cash used in operating activities: Operating leases $ 7,007 $ 5,918 Financing leases $ 354 $ 454 Cash used in financing activities: Financing leases $ 6,080 $ 2,027 ROU assets obtained in exchange for lease obligations: Operating leases $ 3,299 $ 9,268 Financing leases $ 3,941 $ 72
Schedule of Other Information	The following table includes the weighted average remaining lease terms and the weighted average discount rate used to calculate the present value of the Company’s lease liabilities: Other Information September 30, September 30, Weighted average remaining lease term (in years): Operating leases 7.1 8.0 Financing leases 2.8 4.2 Weighted average discount rate: Operating leases 5.1 % 5.2 % Financing leases 5.2 % 5.4 %

DEBT (Tables)

DEBT (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Summary of Convertible Debt	The following table summarizes information regarding the Company’s convertible debt: September 30, December 31, 1.25% senior subordinated convertible notes due in May 2027 (the 2027 Notes) $ 600,000 $ — Unamortized discount (12,792) — Unamortized deferred offering costs (709) — 2027 Notes, net 586,499 — 0.599% senior subordinated convertible notes due in August 2024 (the 2024 Notes) 495,000 495,000 Unamortized discount (5,470) (6,533) Unamortized deferred offering costs (1,865) (2,229) 2024 Notes, net 487,665 486,238 1.50% senior subordinated convertible notes due in October 2020 (the 2020 Notes) 374,993 374,993 Unamortized discount (649) (12,078) Unamortized deferred offering costs (54) (1,033) 2020 Notes, net (1) 374,290 361,882 Total convertible debt, net $ 1,448,454 $ 848,120 Fair value of fixed rate convertible debt (2) : 2027 Notes $ 590,010 $ — 2024 Notes 517,730 521,839 2020 Notes 374,997 405,679 Total fair value of fixed rate convertible debt $ 1,482,737 $ 927,518 (1) The 2020 Notes are classified as a current liability in the periods presented because they matured on October 15, 2020 and were settled in cash for approximately $375.0 million. No shares were issued in connection with the settlement as the Company’s share price did not exceed the conversion price of $94.15, as measured over a 25-day averaging period, and the capped call transaction entered into concurrently with the issuance of notes was not triggered. The Company incurred no gain or loss upon the extinguishment of the 2020 Notes. (2) The fair value of the Company’s fixed-rate convertible debt is based on open market trades and is classified as Level 1 in the fair value hierarchy. For additional discussion of fair value measurements, see Note 3 – Summary of Significant Accounting Policies included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019.
Summary of Interest Expense on Debt	Interest expense on the Company’s convertible debt consisted of the following: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Accretion of discount on convertible notes $ 4,696 $ 4,005 $ 13,201 $ 11,860 Coupon interest expense 4,255 2,271 9,443 6,681 Amortization of debt issuance costs 535 508 1,565 1,522 Total interest expense on convertible debt $ 9,486 $ 6,784 $ 24,209 $ 20,063

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Summary of Amounts Reclassified out of Accumulated Other Comprehensive Income	The following table summarizes amounts reclassified out of AOCI and their effect on the Company’s Condensed Consolidated Statements of Comprehensive Income (Loss) for the three and nine months ended September 30, 2020 and 2019. Condensed Consolidated Three Months Ended Nine Months Ended 2020 2019 2020 2019 Gains (losses) on cash flow hedges: Forward contracts Net product revenues $ 2,693 $ 6,196 $ 17,301 $ 11,171 Forward contracts Operating expenses (815) (1,388) (4,274) (1,885) Total gain (loss) on cash flow hedges $ 1,878 $ 4,808 $ 13,027 $ 9,286
Summary of Changes in Accumulated Balances of AOCI Including Current Period Other Comprehensive Income (Loss) and Reclassifications Out of AOCI	The following tables summarize changes in the accumulated balances for each component of AOCI, including current period other comprehensive income (loss) and reclassifications out of AOCI for the three and nine months ended September 30, 2020 and 2019. Three Months Ended September 30, 2020 Unrealized Gains Unrealized Gains Other Total AOCI balance at June 30, 2020 $ 22,963 $ 7,087 $ — $ 30,050 Other comprehensive income (loss) before reclassifications (16,094) (2,201) — (18,295) Less: net gain (loss) reclassified from AOCI 1,878 — — 1,878 Tax effect — 508 — 508 Net current-period other comprehensive income (loss) (17,972) (1,693) — (19,665) AOCI balance at September 30, 2020 $ 4,991 $ 5,394 $ — $ 10,385 Three Months Ended September 30, 2019 Unrealized Gains Unrealized Gains Other Total AOCI balance at June 30, 2019 $ 14,181 $ 3,271 $ (13) $ 17,439 Other comprehensive income (loss) before 23,973 522 (3) 24,492 Less: gain (loss) reclassified from AOCI 4,808 — — 4,808 Tax effect — (120) — (120) Net current-period other comprehensive income (loss) 19,165 402 (3) 19,564 AOCI balance at September 30, 2019 $ 33,346 $ 3,673 $ (16) $ 37,003 Nine Months Ended September 30, 2020 Unrealized Gains Unrealized Gains Other Total AOCI balance at December 31, 2019 $ 16,614 $ 3,565 $ (15) $ 20,164 Other comprehensive income (loss) before 1,404 2,379 15 3,798 Less: gain (loss) reclassified from AOCI 13,027 — 13,027 Tax effect — (550) — (550) Net current-period other comprehensive income (loss) (11,623) 1,829 15 (9,779) AOCI balance at September 30, 2020 $ 4,991 $ 5,394 $ — $ 10,385 Nine Months Ended September 30, 2019 Unrealized Gains Unrealized Gains Other Total AOCI balance at December 31, 2018 $ 7,201 $ (1,917) $ (13) $ 5,271 Other comprehensive income (loss) before 35,431 7,256 (3) 42,684 Less: gain (loss) reclassified from AOCI 9,286 — — 9,286 Tax effect — (1,666) — (1,666) Net current-period other comprehensive income (loss) 26,145 5,590 (3) 31,732 AOCI balance at September 30, 2019 $ 33,346 $ 3,673 $ (16) $ 37,003

REVENUE, CREDIT CONCENTRATION_2

REVENUE, CREDIT CONCENTRATIONS AND GEOGRAPHIC INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2020
Concentration Risk And Geographic Information [Abstract]
Schedule of Total Revenues from External Customers and Collaborative Partners by Geographic Region	The following table disaggregates Total Revenues from external customers and collaborative partners by geographic region. Net product revenues by geographic region are based on patient location for the Company’s commercial products, except for Aldurazyme, which is sold exclusively to Sanofi Genzyme (Genzyme) who markets and sells Aldurazyme world-wide. Aldurazyme revenues earned by the Company are included in the U.S. region as the transactions are with Genzyme, whose headquarters is located in the U.S. Three Months Ended Nine Months Ended 2020 2019 2020 2019 Total revenues by geographic region: United States $ 252,948 $ 201,874 $ 729,672 $ 562,217 Europe 121,158 125,485 375,453 369,585 Latin America 44,064 83,799 141,852 164,132 Rest of world 58,614 49,939 161,361 153,671 Total revenues $ 476,784 $ 461,097 $ 1,408,338 $ 1,249,605
Schedule of Net Product Revenues by Product	The following table disaggregates Net Product Revenues by product. Three Months Ended Nine Months Ended 2020 2019 2020 2019 Net product revenues by product: Vimizim $ 147,891 $ 163,466 $ 401,789 $ 411,953 Kuvan 123,993 120,524 368,604 340,771 Naglazyme 76,323 94,408 271,585 279,462 Palynziq 46,092 24,142 121,354 55,250 Brineura 25,455 19,840 75,223 46,815 Firdapse — 5,668 1,316 16,262 Total net product revenues marketed by the Company $ 419,754 $ 428,048 $ 1,239,871 $ 1,150,513 Aldurazyme net product revenues marketed by Genzyme 40,987 22,852 $ 128,945 $ 73,945 Total net product revenues $ 460,741 $ 450,900 $ 1,368,816 $ 1,224,458
Schedule of Total Net Product Revenues Based on Patient Location	The table below disaggregates total Net Product Revenues based on patient location for products sold directly by the Company, and global sales of Aldurazyme, which is marketed by Genzyme. Three Months Ended Nine Months Ended 2020 2019 2020 2019 United States $ 203,892 $ 175,127 $ 582,734 $ 480,330 Europe 115,548 121,363 360,718 358,041 Latin America 44,064 83,799 141,852 164,132 Rest of world 56,250 47,759 154,567 148,010 Total net product revenues marketed by the Company 419,754 428,048 1,239,871 1,150,513 Aldurazyme net product revenues marketed by Genzyme 40,987 22,852 128,945 73,945 Total net product revenues $ 460,741 $ 450,900 $ 1,368,816 $ 1,224,458
Schedule of Net Product Revenue Concentrations Attributed to Largest Customers	The following table illustrates the percentage of the Company’s total Net Product Revenues attributed to the Company’s largest customers for the periods presented. Three Months Ended Nine Months Ended 2020 2019 2020 2019 Customer A 16 % 16 % 15 % 17 % Customer B 14 % 13 % 14 % 12 % Customer C 11 % 10 % 12 % 11 % Customer D 1 % 12 % 3 % 6 % Total 42 % 51 % 44 % 46 %

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Stock-Based Compensation Expense	Compensation expense included in the Company’s Condensed Consolidated Statements of Comprehensive Income (Loss) for all stock-based compensation arrangements was as follows: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Cost of sales $ 10,342 $ 4,093 $ 20,381 $ 12,629 Research and development 15,705 14,261 45,333 43,037 Selling, general and administrative 24,122 20,819 76,411 66,097 Total stock-based compensation expense $ 50,169 $ 39,173 $ 142,125 $ 121,763

NET INCOME (LOSS) PER COMMON _2

NET INCOME (LOSS) PER COMMON SHARE (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per common share (common shares in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Numerator: Net Income (Loss), basic $ 784,803 $ 55,036 $ 837,001 $ (38,872) Add: Interest on convertible notes 7,070 937 18,333 — Net Income (Loss), diluted $ 791,873 $ 55,973 $ 855,334 $ (38,872) Denominator: Weighted-average common shares outstanding, basic 181,142 179,289 180,592 178,873 Effect of dilutive securities: Options to purchase common stock 1,731 1,560 1,728 — Common stock issuable under the 2020 notes 3,983 — 3,983 — Common stock issuable under the 2024 notes 3,970 3,970 3,970 — Common stock issuable under the 2027 notes 4,365 — 2,373 — Unvested RSUs 1,926 669 1,765 — Common stock potentially issuable for ESPP purchases 346 231 337 — Common shares held by the NQDC 211 205 211 — Weighted-average common shares outstanding, diluted 197,674 185,924 194,959 178,873 Net Income (Loss) per common share, basic $ 4.33 $ 0.31 4.63 (0.22) Net Income (Loss) per common share, diluted $ 4.01 $ 0.30 4.39 (0.22)
Schedule Of Anti-Dilutive Common Stock Excluded From Computation of Diluted Net Loss Per Share	In addition to the equity instruments included in the table above, the table below presents potential shares of common stock that were excluded from the computation of diluted earnings per common share as they were anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Options to purchase common stock 5,172 5,829 5,175 7,388 Common stock issuable under the 2020 Notes — 3,983 — 3,983 Common stock issuable under the 2024 Notes — — — 3,970 Unvested RSUs 2,900 3,360 3,060 4,029 Common stock potentially issuable for ESPP purchases 193 222 204 453 Common stock held by the NQDC — — — 205 Total number of potentially issuable shares 8,265 13,394 8,439 20,028

Financial Instruments - Schedul

Financial Instruments - Schedule of Cash, Cash Equivalents and Available-for-Sale Securities by Significant Investment Category (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,763,780	$ 1,161,152
Gross Unrealized Gains	7,030	4,713
Gross Unrealized Losses	(15)	(80)
Aggregate Fair Value	1,770,795	1,165,785
Cash and Cash Equivalents	1,015,675	437,446	[1]
Short-term Marketable Securities	489,998	316,361	[1]
Long-term Marketable Securities	265,122	411,978	[1]
Level 1: | Cash
Schedule of Available-for-sale Securities [Line Items]
Cash	378,705	259,347
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Aggregate Fair Value	378,705	259,347
Cash and Cash Equivalents	378,705	259,347
Short-term Marketable Securities	0	0
Long-term Marketable Securities	0	0
Level 2:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,385,075	901,805
Gross Unrealized Gains	7,030	4,713
Gross Unrealized Losses	(15)	(80)
Aggregate Fair Value	1,392,090	906,438
Cash and Cash Equivalents	636,970	178,099
Short-term Marketable Securities	489,998	316,361
Long-term Marketable Securities	265,122	411,978
Level 2: | Money market instruments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	557,006	173,100
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Aggregate Fair Value	557,006	173,100
Cash and Cash Equivalents	557,006	173,100
Short-term Marketable Securities	0	0
Long-term Marketable Securities	0	0
Level 2: | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	435,954	518,523
Gross Unrealized Gains	4,558	3,575
Gross Unrealized Losses	(14)	(12)
Aggregate Fair Value	440,498	522,086
Cash and Cash Equivalents	0	0
Short-term Marketable Securities	280,000	233,294
Long-term Marketable Securities	160,498	288,792
Level 2: | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	361,336	209,633
Gross Unrealized Gains	2,182	993
Gross Unrealized Losses	(1)	(67)
Aggregate Fair Value	363,517	210,559
Cash and Cash Equivalents	79,964	4,999
Short-term Marketable Securities	199,559	83,067
Long-term Marketable Securities	83,994	122,493
Level 2: | Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,430
Gross Unrealized Gains	129
Gross Unrealized Losses	0
Aggregate Fair Value	23,559
Cash and Cash Equivalents	0
Short-term Marketable Securities	3,639
Long-term Marketable Securities	19,920
Level 2: | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,800
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Aggregate Fair Value	6,800
Cash and Cash Equivalents	0
Short-term Marketable Securities	6,800
Long-term Marketable Securities	0
Level 2: | Foreign and other
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	549	549
Gross Unrealized Gains	161	145
Gross Unrealized Losses	0	(1)
Aggregate Fair Value	710	693
Cash and Cash Equivalents	0	0
Short-term Marketable Securities	0	0
Long-term Marketable Securities	$ 710	$ 693
Minimum
Schedule of Available-for-sale Securities [Line Items]
Long term marketable securities maturity period	1 year	1 year
Maximum
Schedule of Available-for-sale Securities [Line Items]
Short term marketable securities maturity period	1 year	1 year
Long term marketable securities maturity period	5 years	5 years
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - Fair Value, Measurements, Recurring $ in Millions	Sep. 30, 2020USD ($)investment	Dec. 31, 2019USD ($)
Schedule of Available-for-sale Securities [Line Items]
Number of investments | investment	3
Strategic Investment
Schedule of Available-for-sale Securities [Line Items]
Strategic investments fair value | $	$ 8	$ 6.2

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Intangible assets:
Finite-lived intangible assets	$ 638,468	$ 652,734
Accumulated amortization	(211,296)	(196,154)
Net carrying value	$ 427,172	$ 456,580	[1]
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jan. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Gain (loss) on disposition of other assets			$ 59,495	$ 15,000
Finite-lived intangible assets			638,468			$ 652,734
Accumulated amortization			$ 211,296			$ 196,154
Gain on sale of nonfinancial assets		$ 15,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Firdapse
Goodwill [Line Items]
Cash payment					$ 67,200
Gain (loss) on disposition of other assets	$ 59,500
Increase (decrease) in goodwill	(800)
Finite-lived intangible assets	32,200
Accumulated amortization	$ 31,600

Property Plant and Equipment -

Property Plant and Equipment - Schedule of Property Plant and Equipment Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,628,745	$ 1,559,968
Accumulated depreciation	(613,683)	(549,100)
Total property, plant and equipment, net	1,015,062	1,010,868	[1]
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	756,479	725,906
Manufacturing and laboratory equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	402,357	366,951
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	187,722	167,554
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,349	7,349
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	90,418	90,418
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	52,479	51,324
Land improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	39,360	38,569
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 92,581	$ 111,897
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - Schedule of Depreciation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 22,187	$ 24,238	$ 65,749	$ 67,206
Depreciation capitalized into inventory	$ 10,883	$ 9,807	$ 34,053	$ 24,894

Supplemental Balance Sheet In_3

Supplemental Balance Sheet Information - Schedule of Inventory (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Inventory [Line Items]
Raw materials	$ 73,857,000		$ 73,857,000		$ 74,442,000
Work-in-process	296,685,000		296,685,000		349,978,000
Finished goods	330,305,000		330,305,000		255,855,000
Total inventory	700,847,000		700,847,000		$ 680,275,000	[1]
Cost of sales	188,793,000	$ 96,949,000	398,134,000	$ 263,567,000
Pre-Launch Valoctocogene Roxaparvovec
Inventory [Line Items]
Total inventory	0		0
Cost of sales	$ 81,200,000		$ 81,200,000
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

Supplemental Balance Sheet In_4

Supplemental Balance Sheet Information - Schedule of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts payable and accrued operating expenses	$ 218,021	$ 240,981
Accrued compensation expense	137,415	192,467
Accrued rebates payable	65,999	57,163
Accrued royalties payable	20,426	30,797
Lease liabilities	10,930	10,700
Value added taxes payable	7,222	8,395
Forward foreign currency exchange contracts	7,774	10,448
Deferred revenue	3,240	13,037
Other	9,376	6,633
Total accounts payable and accrued liabilities	$ 480,403	$ 570,621	[1]
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Financial Assets and Liabilities (Detail) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Quoted Price in Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets remeasured	$ 0	$ 0
Liabilities remeasured	0	0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	20,639,000	19,456,000
Fair value of financial assets, Total	22,541,000	20,633,000
Fair value of other non-current liabilities	71,755,000	67,081,000
Fair value of financial liabilities, Total	73,657,000	68,258,000
Fair Value, Measurements, Recurring | NQDC Plan liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	1,902,000	1,177,000
Fair value of other non-current liabilities	17,652,000	16,288,000
Fair Value, Measurements, Recurring | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current liabilities	54,103,000	50,793,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	20,639,000	19,456,000
Fair value of financial assets, Total	22,541,000	20,633,000
Fair value of other non-current liabilities	17,652,000	16,288,000
Fair value of financial liabilities, Total	19,554,000	17,465,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | NQDC Plan liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	1,902,000	1,177,000
Fair value of other non-current liabilities	17,652,000	16,288,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current liabilities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	0	0
Fair value of financial assets, Total	0	0
Fair value of other non-current liabilities	54,103,000	50,793,000
Fair value of financial liabilities, Total	54,103,000	50,793,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | NQDC Plan liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	0	0
Fair value of other non-current liabilities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current liabilities	54,103,000	50,793,000
Fair Value, Measurements, Recurring | NQDC Plan assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	1,902,000	1,177,000
Fair value of other non-current assets	17,652,000	16,288,000
Fair Value, Measurements, Recurring | NQDC Plan assets | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	1,902,000	1,177,000
Fair value of other non-current assets	17,652,000	16,288,000
Fair Value, Measurements, Recurring | NQDC Plan assets | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	0	0
Fair value of other non-current assets	0	0
Fair Value, Measurements, Recurring | Restricted Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	2,987,000	3,168,000
Fair Value, Measurements, Recurring | Restricted Investments | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	2,987,000	3,168,000
Fair Value, Measurements, Recurring | Restricted Investments | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	$ 0	$ 0

Fair Value Measurements - Liabi

Fair Value Measurements - Liabilities Measured at Fair Value on Recurring Basis Using Level 3 Inputs (Detail) - Contingent Payment $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration at December 31, 2019	$ 50,793
Changes in fair value of contingent consideration	1,352
Foreign exchange remeasurement of Euro denominated contingent acquisition consideration	1,958
Contingent consideration at September 30, 2020	$ 54,103

Derivative Instruments and He_3

Derivative Instruments and Hedging Strategies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Derivative [Line Items]
Amount reclassified from AOCI to earnings as related to forecasted revenue and operating expense transactions	$ 4.8
Derivatives Designated As Hedging Instruments
Derivative [Line Items]
Maturity of derivatives	2 years 6 months
Not Designated as Hedging Instrument
Derivative [Line Items]
Maturity of derivatives	3 months

Derivative Instruments and He_4

Derivative Instruments and Hedging Strategies - Summary of Derivatives Designated as Hedging Instruments Outstanding (Detail) - Derivatives Designated As Hedging Instruments - Foreign exchange contracts - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Sell
Derivative [Line Items]
Notional amount	$ 729,998	$ 820,546
Purchase
Derivative [Line Items]
Notional amount	$ 163,116	$ 212,348

Derivative Instruments and He_5

Derivative Instruments and Hedging Strategies - Summary of Derivatives Not Designated as Hedging Instruments Outstanding (Detail) - Not Designated as Hedging Instrument - Foreign exchange contracts - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Sell
Derivative [Line Items]
Notional amount	$ 41,031	$ 77,335
Purchase
Derivative [Line Items]
Notional amount	$ 30,031	$ 30,818

Derivative Instruments and He_6

Derivative Instruments and Hedging Strategies - Fair Value Carrying Amount of Derivatives (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative asset, fair value	$ 18,174	$ 33,592
Derivative liability, fair value	12,180	15,941
Level 2: | Derivatives Designated As Hedging Instruments
Derivative [Line Items]
Derivative asset, fair value	18,158	33,123
Derivative liability, fair value	12,110	13,677
Level 2: | Derivatives Designated As Hedging Instruments | Other current assets
Derivative [Line Items]
Derivative asset, fair value	13,537	19,584
Level 2: | Derivatives Designated As Hedging Instruments | Other assets
Derivative [Line Items]
Derivative asset, fair value	4,621	13,539
Level 2: | Derivatives Designated As Hedging Instruments | Accounts payable and accrued liabilities
Derivative [Line Items]
Derivative liability, fair value	7,704	8,184
Level 2: | Derivatives Designated As Hedging Instruments | Other long-term liabilities
Derivative [Line Items]
Derivative liability, fair value	4,406	5,493
Level 2: | Not Designated as Hedging Instrument | Other current assets
Derivative [Line Items]
Derivative asset, fair value	16	469
Level 2: | Not Designated as Hedging Instrument | Accounts payable and accrued liabilities
Derivative [Line Items]
Derivative liability, fair value	$ 70	$ 2,264

Derivative Instruments and He_7

Derivative Instruments and Hedging Strategies - Summary of Impact of Gains and Losses from Derivatives Designated as Hedging Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Net product revenues	$ 476,784	$ 461,097	$ 1,408,338	$ 1,249,605
Operating expenses as reported	532,725	457,087	1,400,263	1,340,900
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) Recognized in Earnings	4,166	(1,286)	9,600	(5,182)
Operating expenses as reported | Derivatives Designated As Hedging Instruments | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Derivative Instruments, Gain (Loss) [Line Items]
Cash Flow Hedging Gains (Losses) Reclassified into Earnings	(815)	(1,388)	(4,274)	(1,885)
Net product revenues
Derivative Instruments, Gain (Loss) [Line Items]
Net product revenues	460,741	450,900	1,368,816	1,224,458
Net product revenues | Derivatives Designated As Hedging Instruments | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Derivative Instruments, Gain (Loss) [Line Items]
Cash Flow Hedging Gains (Losses) Reclassified into Earnings	$ 2,693	$ 6,196	$ 17,301	$ 11,171

Leases - Schedule of ROU Assets

Leases - Schedule of ROU Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Operating	$ 45,764	$ 49,045
Financing	12,018	10,389
Total ROU assets	57,782	59,434
Liabilities:
Operating, current	7,813	7,451
Financing, current	3,117	3,249
Operating, noncurrent	40,831	44,092
Financing, noncurrent	4,570	6,708
Total lease liabilities	$ 56,331	$ 61,500
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Operating
Remainder of 2020	$ 3,460
2021	9,908
2022	9,095
2023	8,055
2024	6,253
Thereafter	21,714
Total lease payments	58,485
Less: Interest	(9,841)
Present value of lease liabilities	48,644
Financing
Remainder of 2020	940
2021	3,080
2022	2,375
2023	1,797
2024	48
Thereafter	20
Total lease payments	8,260
Less: Interest	(573)
Present value of lease liabilities	7,687
Total
Remainder of 2020	4,400
2021	12,988
2022	11,470
2023	9,852
2024	6,301
Thereafter	21,734
Total lease payments	66,745
Less: Interest	(10,414)
Present value of lease liabilities	$ 56,331	$ 61,500

Leases - Schedule of Lease Cost

Leases - Schedule of Lease Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lease Cost
Total lease costs	$ 4,179	$ 4,277	$ 11,612	$ 12,212
Operating Expenses
Lease Cost
Operating	3,227	3,535	8,953	9,946
Amortization	841	600	2,307	1,811
Interest expense	$ 111	$ 142	$ 352	$ 455

Leases - Schedule of Other Info

Leases - Schedule of Other Information (Detail) - lease	Sep. 30, 2020	Sep. 30, 2019
Weighted average remaining lease term (in years):
Operating leases	7 years 1 month 6 days	8 years
Financing leases	2 years 9 months 18 days	4 years 2 months 12 days
Weighted average discount rate:
Operating leases	5.10%	5.20%
Financing leases	5.20%	5.40%
Additional leases not yet commenced (undiscounted):
Operating leases expected to commence in remainder of year	1

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash used in operating activities:
Operating leases	$ 7,007	$ 5,918
Financing leases	354	454
Cash used in financing activities:
Financing leases	6,080	2,027
ROU assets obtained in exchange for lease obligations:
Operating leases	3,299	9,268
Financing leases	$ 3,941	$ 72

Debt - Additional Information (

Debt - Additional Information (Detail)	1 Months Ended
	May 31, 2020USD ($)$ / shares	Oct. 31, 2018USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Carrying value of equity component			$ 1,500,000,000
1.25% Senior Subordinated Convertible Notes Due in May 2027
Debt Instrument [Line Items]
Carrying value of equity component			$ 600,000,000	$ 0
Convertible notes stated rate			1.25%	1.25%
Debt discount			$ 12,792,000	$ 0
1.25% Senior Subordinated Convertible Notes Due in May 2027 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt face amount	$ 600,000,000
Convertible notes stated rate	1.25%
Debt instrument, conversion ratio	7.2743
Debt instrument, convertible, conversion price, per share (in dollars per share) | $ / shares	$ 137.47
Proceeds from issuance of notes	$ 585,800,000
Debt discount	13,500,000
Debt issuance costs	$ 700,000
The 2018 Credit Facility
Debt Instrument [Line Items]
Debt issuance costs		$ 1,000,000
Maximum borrowing capacity		$ 200,000,000
Outstanding amount			0	0
The 2018 Credit Facility | Minimum
Debt Instrument [Line Items]
Percentage of commitment fees payable on undrawn amount		0.15%
The 2018 Credit Facility | Minimum | LIBOR Rate
Debt Instrument [Line Items]
Debt instrument interest rate percentage		1.00%
The 2018 Credit Facility | Minimum | Base Rate
Debt Instrument [Line Items]
Debt instrument interest rate percentage		0.00%
The 2018 Credit Facility | Maximum
Debt Instrument [Line Items]
Percentage of commitment fees payable on undrawn amount		0.35%
The 2018 Credit Facility | Maximum | LIBOR Rate
Debt Instrument [Line Items]
Debt instrument interest rate percentage		1.95%
The 2018 Credit Facility | Maximum | Base Rate
Debt Instrument [Line Items]
Debt instrument interest rate percentage		0.95%
1.50% Senior Subordinated Convertible Notes Due in October 2020
Debt Instrument [Line Items]
Carrying value of equity component			$ 374,993,000	$ 374,993,000
Convertible notes stated rate			1.50%	1.50%
Debt discount			$ 649,000	$ 12,078,000

Debt - Summary of Convertible D

Debt - Summary of Convertible Debt (Detail) $ / shares in Units, $ in Thousands	Oct. 15, 2020USD ($)d$ / sharesshares	Sep. 30, 2020USD ($)	May 31, 2020USD ($)$ / shares	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Convertible Notes		$ 1,500,000
Convertible Notes, net of unamortized discount and deferred offering costs		1,074,164		$ 486,238	[1]
Short-term convertible debt, net		374,290		361,882	[1]
Total convertible debt, net		1,448,454		848,120
Total fair value of fixed rate convertible debt		$ 1,482,737		$ 927,518
1.25% Senior Subordinated Convertible Notes Due in May 2027
Debt Instrument [Line Items]
Convertible notes stated rate		1.25%		1.25%
Convertible Notes		$ 600,000		$ 0
Convertible debt, unamortized discount		(12,792)		0
Convertible debt, Unamortized deferred offering costs		(709)		0
Convertible Notes, net of unamortized discount and deferred offering costs		586,499		0
Total fair value of fixed rate convertible debt		$ 590,010		$ 0
1.25% Senior Subordinated Convertible Notes Due in May 2027 | Senior Subordinated Notes
Debt Instrument [Line Items]
Convertible notes stated rate			1.25%
Convertible debt, unamortized discount			$ (13,500)
Debt instrument, convertible, conversion price, per share (in dollars per share) | $ / shares			$ 137.47
0.599% Senior Subordinated Convertible Notes Due in August 2024
Debt Instrument [Line Items]
Convertible notes stated rate		0.599%		0.599%
Convertible Notes		$ 495,000		$ 495,000
Convertible debt, unamortized discount		(5,470)		(6,533)
Convertible debt, Unamortized deferred offering costs		(1,865)		(2,229)
Convertible Notes, net of unamortized discount and deferred offering costs		487,665		486,238
Total fair value of fixed rate convertible debt		$ 517,730		$ 521,839
1.50% Senior Subordinated Convertible Notes Due in October 2020
Debt Instrument [Line Items]
Convertible notes stated rate		1.50%		1.50%
Convertible Notes		$ 374,993		$ 374,993
Convertible debt, unamortized discount		(649)		(12,078)
Convertible debt, Unamortized deferred offering costs		(54)		(1,033)
Short-term convertible debt, net		374,290		361,882
Total fair value of fixed rate convertible debt		$ 374,997		$ 405,679
1.50% Senior Subordinated Convertible Notes Due in October 2020 | Subsequent Event
Debt Instrument [Line Items]
Repayments of convertible debt	$ 375,000
Shares issued (in shares) | shares	0
Measurement period | d	25
1.50% Senior Subordinated Convertible Notes Due in October 2020 | Subsequent Event | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, convertible, conversion price, per share (in dollars per share) | $ / shares	$ 94.15
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

Debt - Summary of Interest Expe

Debt - Summary of Interest Expense on Convertible Debt (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule Of Interest Expenses [Line Items]
Total interest expense on convertible debt	$ 9,597	$ 2,937	$ 24,560	$ 16,530
Convertible Senior Notes
Schedule Of Interest Expenses [Line Items]
Accretion of discount on convertible notes	4,696	4,005	13,201	11,860
Coupon interest expense	4,255	2,271	9,443	6,681
Amortization of debt issuance costs	535	508	1,565	1,522
Total interest expense on convertible debt	$ 9,486	$ 6,784	$ 24,209	$ 20,063

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income - Amounts Reclassified out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net product revenues	$ 476,784	$ 461,097	$ 1,408,338	$ 1,249,605
INCOME (LOSS) FROM OPERATIONS	(55,941)	4,010	8,075	(91,295)
Net product revenues
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net product revenues	460,741	450,900	1,368,816	1,224,458
Amount Reclassified from AOCI Gain (Loss) | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
INCOME (LOSS) FROM OPERATIONS	1,878	4,808	13,027	9,286
Amount Reclassified from AOCI Gain (Loss) | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Forward contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating expenses	(815)	(1,388)	(4,274)	(1,885)
Amount Reclassified from AOCI Gain (Loss) | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Net product revenues | Forward contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net product revenues	$ 2,693	$ 6,196	$ 17,301	$ 11,171

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income - Summary of Changes in Accumulated Balances of AOCI Including Current Period Other Comprehensive Income (Loss) and Reclassifications Out of AOCI (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020		Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	$ 3,236,679	$ 2,960,954	$ 3,122,381	[2]	$ 2,967,940
Other comprehensive income (loss) before      reclassifications		(18,295)	24,492	3,798		42,684
Less: net gain (loss) reclassified from AOCI		1,878	4,808	13,027		9,286
Tax effect		508	(120)	(550)		(1,666)
Net current-period other comprehensive income (loss)		(19,665)	19,564	(9,779)		31,732
Ending balance		4,053,893	3,074,405	4,053,893		3,074,405
Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		22,963	14,181	16,614		7,201
Other comprehensive income (loss) before      reclassifications		(16,094)	23,973	1,404		35,431
Less: net gain (loss) reclassified from AOCI		1,878	4,808	13,027		9,286
Tax effect		0	0	0		0
Net current-period other comprehensive income (loss)		(17,972)	19,165	(11,623)		26,145
Ending balance		4,991	33,346	4,991		33,346
Unrealized Gains (Losses) on Available for-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		7,087	3,271	3,565		(1,917)
Other comprehensive income (loss) before      reclassifications		(2,201)	522	2,379		7,256
Less: net gain (loss) reclassified from AOCI		0	0			0
Tax effect		508	(120)	(550)		(1,666)
Net current-period other comprehensive income (loss)		(1,693)	402	1,829		5,590
Ending balance		5,394	3,673	5,394		3,673
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		0	(13)	(15)		(13)
Other comprehensive income (loss) before      reclassifications		0	(3)	15		(3)
Less: net gain (loss) reclassified from AOCI		0	0	0		0
Tax effect		0	0	0		0
Net current-period other comprehensive income (loss)		0	(3)	15		(3)
Ending balance		0	(16)	0		(16)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	30,050	17,439	20,164		5,271
Ending balance		$ 10,385	$ 37,003	$ 10,385		$ 37,003
[1]	The beginning balances for the nine-month periods were derived from the audited Consolidated Financial Statements included in Company’s Annual Report on Form 10-K for the years ended December 31, 2019 and 2018, respectively, filed with the SEC on February 27, 2020.
[2]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

Revenue, Credit Concentration_3

Revenue, Credit Concentrations and Geographic Information - Additional Information (Detail) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020USD ($)Segment	Dec. 31, 2019USD ($)
Concentration Risk And Geographic Information [Line Items]
Number of operating business segment | Segment	1
Accounts receivable, net	$ 411,712	$ 377,404	[1]
Customers
Concentration Risk And Geographic Information [Line Items]
Accounts receivable, net	$ 106,500	$ 60,200
Credit Concentration Risk | Accounts Receivable | Customer One
Concentration Risk And Geographic Information [Line Items]
Concentration risk, percentage	33.00%	24.00%
Credit Concentration Risk | Accounts Receivable | Customer Two
Concentration Risk And Geographic Information [Line Items]
Concentration risk, percentage	15.00%	16.00%
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

Revenue, Credit Concentration_4

Revenue, Credit Concentrations and Geographic Information - Disaggregates of Total Revenues from External Customers and Collaborative Partners by Geographic Region (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer [Line Items]
Total revenues	$ 476,784	$ 461,097	$ 1,408,338	$ 1,249,605
United States
Revenue from External Customer [Line Items]
Total revenues	252,948	201,874	729,672	562,217
Europe
Revenue from External Customer [Line Items]
Total revenues	121,158	125,485	375,453	369,585
Latin America
Revenue from External Customer [Line Items]
Total revenues	44,064	83,799	141,852	164,132
Rest of world
Revenue from External Customer [Line Items]
Total revenues	$ 58,614	$ 49,939	$ 161,361	$ 153,671

Revenue, Credit Concentration_5

Revenue, Credit Concentrations and Geographic Information - Disaggregates of Net Product Revenues by Product (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer [Line Items]
Net product revenues	$ 476,784	$ 461,097	$ 1,408,338	$ 1,249,605
Vimizim | Marketed by Company
Revenue from External Customer [Line Items]
Net product revenues	147,891	163,466	401,789	411,953
Kuvan | Marketed by Company
Revenue from External Customer [Line Items]
Net product revenues	123,993	120,524	368,604	340,771
Naglazyme | Marketed by Company
Revenue from External Customer [Line Items]
Net product revenues	76,323	94,408	271,585	279,462
Palynziq | Marketed by Company
Revenue from External Customer [Line Items]
Net product revenues	46,092	24,142	121,354	55,250
Brineura | Marketed by Company
Revenue from External Customer [Line Items]
Net product revenues	25,455	19,840	75,223	46,815
Firdapse | Marketed by Company
Revenue from External Customer [Line Items]
Net product revenues	0	5,668	1,316	16,262
Total net product revenues
Revenue from External Customer [Line Items]
Net product revenues	460,741	450,900	1,368,816	1,224,458
Total net product revenues | Marketed by Company
Revenue from External Customer [Line Items]
Net product revenues	419,754	428,048	1,239,871	1,150,513
Aldurazyme | Marketed by Genzyme
Revenue from External Customer [Line Items]
Net product revenues	$ 40,987	$ 22,852	$ 128,945	$ 73,945

Revenue, Credit Concentration_6

Revenue, Credit Concentrations and Geographic Information - Disaggregates of Total Net Product Revenues Based on Patient Location (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Net product revenues	$ 476,784	$ 461,097	$ 1,408,338	$ 1,249,605
United States
Disaggregation of Revenue [Line Items]
Net product revenues	252,948	201,874	729,672	562,217
Europe
Disaggregation of Revenue [Line Items]
Net product revenues	121,158	125,485	375,453	369,585
Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	44,064	83,799	141,852	164,132
Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	58,614	49,939	161,361	153,671
Total net product revenues
Disaggregation of Revenue [Line Items]
Net product revenues	460,741	450,900	1,368,816	1,224,458
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim
Disaggregation of Revenue [Line Items]
Net product revenues	419,754	428,048	1,239,871	1,150,513
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim | United States
Disaggregation of Revenue [Line Items]
Net product revenues	203,892	175,127	582,734	480,330
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim | Europe
Disaggregation of Revenue [Line Items]
Net product revenues	115,548	121,363	360,718	358,041
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim | Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	44,064	83,799	141,852	164,132
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim | Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	56,250	47,759	154,567	148,010
Marketed by Company | Total net product revenues
Disaggregation of Revenue [Line Items]
Net product revenues	419,754	428,048	1,239,871	1,150,513
Marketed by Genzyme | Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	$ 40,987	$ 22,852	$ 128,945	$ 73,945

Revenue, Credit Concentration_7

Revenue, Credit Concentrations and Geographic Information - Total Net Product Revenue Concentrations Attributed to Largest Customers (Detail) - Customer Concentration Risk - Net Product Revenue	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Concentration Risk [Line Items]
Concentration risk, percentage	42.00%	51.00%	44.00%	46.00%
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	16.00%	16.00%	15.00%	17.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage	14.00%	13.00%	14.00%	12.00%
Customer C
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%	10.00%	12.00%	11.00%
Customer D
Concentration Risk [Line Items]
Concentration risk, percentage	1.00%	12.00%	3.00%	6.00%

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 50,169	$ 39,173	$ 142,125	$ 121,763
Cost of sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	10,342	4,093	20,381	12,629
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	15,705	14,261	45,333	43,037
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 24,122	$ 20,819	$ 76,411	$ 66,097

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense capitalized to inventory		$ 4.9	$ 5.1	$ 14.9	$ 13.2
Restricted Stock Unit Awards With Market Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted restricted stock units (in shares)	126,710
Award vesting service period	3 years
Base percentage of annual target ceiling	100.00%
Weighted-average fair value per RSU granted (in dollars per share)	$ 112.12
Restricted Stock Unit Awards With Market Conditions | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of shares earned, performance metric	0.00%
Percentage of Annual TSR multiplier on absolute basis	50.00%
Restricted Stock Unit Awards With Market Conditions | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of shares earned, performance metric	200.00%
Restricted Stock Unit Awards With Performance Conditions, Non-GAAP Income Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted restricted stock units (in shares)	63,400
Award vesting service period	3 years
Weighted-average fair value per RSU granted (in dollars per share)	$ 73.82
Restricted Stock Unit Awards With Performance Conditions, Non-GAAP Income Target | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of shares earned, performance metric	50.00%
Restricted Stock Unit Awards With Performance Conditions, Non-GAAP Income Target | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of shares earned, performance metric	200.00%
Restricted Stock Unit Awards With Performance Conditions, Strategic Goal Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted restricted stock units (in shares)	63,400
Award vesting service period	3 years
Weighted-average fair value per RSU granted (in dollars per share)	$ 73.82
Restricted Stock Unit Awards With Performance Conditions, Strategic Goal Target | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of shares earned, performance metric	50.00%
Restricted Stock Unit Awards With Performance Conditions, Strategic Goal Target | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of shares earned, performance metric	200.00%

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	[1]
Income Tax Contingency [Line Items]
Deferred tax assets	$ 1,396,547	$ 549,422
IRELAND
Income Tax Contingency [Line Items]
Deferred tax assets	$ 835,100
[1]	December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.

NET INCOME (LOSS) PER COMMON _3

NET INCOME (LOSS) PER COMMON SHARE - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net Income (Loss), basic	$ 784,803	$ 55,036	$ 837,001	$ (38,872)
Add: Interest on convertible notes	7,070	937	18,333	0
Net Income (Loss), diluted	$ 791,873	$ 55,973	$ 855,334	$ (38,872)
Denominator:
Weighted average number of shares outstanding, basic	181,142	179,289	180,592	178,873
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Weighted-average common shares outstanding, diluted	197,674	185,924	194,959	178,873
Net Income (Loss) per common share, basic (in dollars per share)	$ 4.33	$ 0.31	$ 4.63	$ (0.22)
Net Income (Loss) per common share, diluted (in dollars per share)	$ 4.01	$ 0.30	$ 4.39	$ (0.22)
Options to purchase common stock
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	1,731	1,560	1,728	0
Common stock issuable under the 2020 notes
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	3,983	0	3,983	0
Common stock issuable under the 2024 notes
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	3,970	3,970	3,970	0
Common stock issuable under the 2027 Notes
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	4,365	0	2,373	0
Unvested restricted stock units
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	1,926	669	1,765	0
Common stock potentially issuable for ESPP purchases
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	346	231	337	0
Common stock held by the NQDC
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	211	205	211	0

NET INCOME (LOSS) PER COMMON _4

NET INCOME (LOSS) PER COMMON SHARE - Schedule Of Anti-Dilutive Common Stock Excluded From Computation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	8,265	13,394	8,439	20,028
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	5,172	5,829	5,175	7,388
Common stock issuable under the 2020 notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	0	3,983	0	3,983
Common stock issuable under the 2024 notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	0	0	0	3,970
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	2,900	3,360	3,060	4,029
Common stock potentially issuable for ESPP purchases
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	193	222	204	453
Common stock held by the NQDC
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	0	0	0	205

NET INCOME (LOSS) PER COMMON _5

NET INCOME (LOSS) PER COMMON SHARE - Additional Information (Detail)	Sep. 30, 2020$ / shares
Convertible Notes due 2020
Earnings Per Share [Line Items]
Debt instrument, convertible, conversion price, per share (in dollars per share)	$ 94.15

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2020	Sep. 30, 2020
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain development and regulatory activities and commercial sales and licensing milestones		$ 622.4
Contingent liabilities		54.1
Clinical and Post Marketing Services
Commitments And Contingencies [Line Items]
Purchase commitments and other minimum contractual obligations		150.3
Third Party
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain development and regulatory activities and commercial sales and licensing milestones		70.3
Early Stage Development Program | Third Party
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain development and regulatory activities and commercial sales and licensing milestones	$ 235
Programs No Longer Being Developed | Third Party
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain development and regulatory activities and commercial sales and licensing milestones		$ 236