BioMarin Pharmaceutical (BMRN) 10-Q 29 Oct 19 2019 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2019	Oct. 18, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
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		179,625,303
Amendment Flag	false
Document Fiscal Year Focus	2019
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, 2019	Dec. 31, 2018	[1]
Current assets:
Cash and cash equivalents	$ 423,220	$ 493,982
Short-term investments	297,572	590,326
Accounts receivable, net	402,970	342,633
Inventory	609,049	530,871
Other current assets	126,548	98,403
Total current assets	1,859,359	2,056,215
Noncurrent assets:
Long-term investments	431,804	235,864
Property, plant and equipment, net	969,300	948,682
Intangible assets, net	462,849	491,808
Goodwill	197,039	197,039
Deferred tax assets	525,131	460,952
Other assets	112,646	36,568
Total assets	4,558,128	4,427,128
Current liabilities:
Accounts payable and accrued liabilities	483,745	437,290
Short-term contingent consideration	10,000	85,951
Total current liabilities	493,745	523,241
Noncurrent liabilities:
Long-term convertible debt, net	843,616	830,417
Long-term contingent consideration	48,930	46,883
Other long-term liabilities	97,432	58,647
Total liabilities	1,483,723	1,459,188
Stockholders’ equity:
Common stock, $0.001 par value: 500,000,000 shares authorized; 179,604,381 and 178,252,954 shares issued and outstanding, respectively.	180	178
Additional paid-in capital	4,782,916	4,669,926
Company common stock held by Nonqualified Deferred Compensation Plan (the NQDC)	(9,961)	(13,301)
Accumulated other comprehensive income	37,003	5,271
Accumulated deficit	(1,735,733)	(1,694,134)
Total stockholders’ equity	3,074,405	2,967,940	[2]
Total liabilities and stockholders’ equity	$ 4,558,128	$ 4,427,128
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.
[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 year ended December 31, 2018 , filed with the SEC on February 28, 2019.

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
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)	179,604,381	178,252,954
Common stock, shares outstanding (in shares)	179,604,381	178,252,954

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
REVENUES:
Total revenues	$ 461,097	$ 391,706	$ 1,249,605	$ 1,137,998
OPERATING EXPENSES:
Cost of sales	96,949	78,893	263,567	240,245
Research and development	172,963	161,408	542,195	520,938
Selling, general and administrative	170,112	148,566	493,024	440,182
Intangible asset amortization and contingent consideration	17,063	18,580	57,114	42,009
Gain on sale of intangible assets	0	0	(15,000)	(20,000)
Total operating expenses	457,087	407,447	1,340,900	1,223,374
INCOME (LOSS) FROM OPERATIONS	4,010	(15,741)	(91,295)	(85,376)
Equity in the loss of BioMarin/Genzyme LLC	(551)	(468)	(780)	(507)
Interest income	5,340	6,338	17,537	17,141
Interest expense	(2,937)	(12,131)	(16,530)	(35,918)
Other income, net	3,960	2,589	6,038	5,266
INCOME (LOSS) BEFORE INCOME TAXES	9,822	(19,413)	(85,030)	(99,394)
Benefit from income taxes	(45,214)	(6,793)	(46,158)	(25,833)
NET INCOME (LOSS)	$ 55,036	$ (12,620)	$ (38,872)	$ (73,561)
NET INCOME (LOSS) PER SHARE, BASIC (in dollars per share)	$ 0.31	$ (0.07)	$ (0.22)	$ (0.42)
NET INCOME (LOSS) PER SHARE, DILUTED (in dollars per share)	$ 0.30	$ (0.07)	$ (0.22)	$ (0.42)
Weighted average common shares outstanding, basic (in shares)	179,289	177,481	178,873	176,767
Weighted average common shares outstanding, diluted (in shares)	185,924	177,481	178,873	176,767
COMPREHENSIVE INCOME (LOSS)	$ 74,600	$ (13,651)	$ (7,140)	$ (52,174)
Net product revenues
REVENUES:
Total revenues	450,900	386,320	1,224,458	1,123,205
Royalty and other revenues
REVENUES:
Total revenues	$ 10,197	$ 5,386	$ 25,147	$ 14,793

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total		Common Stock	Additional Paid-in Capital	Company Stock Held By NQDC	Accumulated other comprehensive income (loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017	[1]			175,844,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				2,059,000
Ending balance (in shares) at Sep. 30, 2018				177,903,000
Beginning Balance at Dec. 31, 2017	[1]	$ 2,808,663		$ 176	$ 4,483,220	$ (14,224)	$ (22,961)	$ (1,637,548)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				2	21,461
Stock-based compensation					116,136
Common stock held by the NQDC						809
Accounting impact of NQDC Plan change					0	0
Other comprehensive income (loss)							21,387
Net income (loss)		(73,561)						(73,561)
Ending Balance at Sep. 30, 2018		2,914,945		$ 178	4,620,817	(13,415)	(2,160)	(1,690,475)
Beginning balance (in shares) at Jun. 30, 2018	[1]			177,508,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				395,000
Ending balance (in shares) at Sep. 30, 2018				177,903,000
Beginning Balance at Jun. 30, 2018	[1]	2,885,104		$ 178	4,577,300	(13,390)	(1,129)	(1,677,855)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				0	5,151
Stock-based compensation					38,366
Common stock held by the NQDC					0	(25)
Accounting impact of NQDC Plan change					0	0
Other comprehensive income (loss)							(1,031)
Net income (loss)		(12,620)						(12,620)
Ending Balance at Sep. 30, 2018		2,914,945		$ 178	4,620,817	(13,415)	(2,160)	(1,690,475)
Beginning balance (in shares) at Dec. 31, 2018	[1]			178,253,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				1,351,000
Ending balance (in shares) at Sep. 30, 2019				179,604,000
Beginning Balance at Dec. 31, 2018	[1]	2,967,940	[2]	$ 178	4,669,926	(13,301)	5,271	(1,694,134)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				2	(19,183)
Stock-based compensation					122,212
Common stock held by the NQDC					(692)	692
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	(9,961)	37,003	(1,735,733)
Beginning balance (in shares) at Jun. 30, 2019	[1]			179,433,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				171,000
Ending balance (in shares) at Sep. 30, 2019				179,604,000
Beginning Balance at Jun. 30, 2019	[1]	2,960,954		$ 179	4,744,316	(10,211)	17,439	(1,790,769)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				1	(1,294)
Stock-based compensation					40,144
Common stock held by the NQDC					(250)	250
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	$ (9,961)	$ 37,003	$ (1,735,733)
[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 year ended December 31, 2018 , filed with the SEC on February 28, 2019.
[2]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (38,872)		$ (73,561)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	79,510		70,955
Non-cash interest expense	9,395		26,099
(Accretion of discount) Amortization of premium on investments	(1,897)		769
Stock-based compensation	121,763		112,261
Gain on sale of intangible assets	(15,000)		(20,000)
Deferred income taxes	(59,780)		(32,735)
Unrealized foreign exchange (gain) loss	784		(11,997)
Non-cash changes in the fair value of contingent consideration	5,646		12,836
Other	(18)		(459)
Changes in operating assets and liabilities:
Accounts receivable, net	(61,803)		(95,884)
Inventory	(52,571)		(10,232)
Other current assets	(13,259)		4,276
Other assets	(7,112)		(3,148)
Accounts payable and accrued liabilities	21,747		(12,090)
Other long-term liabilities	2,386		3,744
Net cash used in operating activities	(9,081)		(29,166)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	(94,241)		(102,541)
Maturities and sales of investments	635,678		857,063
Purchases of available-for-sale securities	(528,497)		(439,198)
Proceeds from sale of intangible assets	15,000		20,000
Purchase of intangible assets	(8,323)		0
Other	(1,747)		(10)
Net cash provided by investing activities	17,870		335,314
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercises of awards under equity incentive plans	21,768		55,643
Taxes paid related to net share settlement of equity awards	(40,951)		(34,180)
Payment of contingent acquisition consideration	(57,508)		(43,108)
Other	(2,025)		0
Net cash used in financing activities	(78,716)		(21,645)
Effect of exchange rate changes on cash	(835)		(347)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(70,762)		284,156
Cash and cash equivalents:
Beginning of period	493,982	[1]	598,028
End of period	423,220		882,184
SUPPLEMENTAL CASH FLOW DISCLOSURES:
Cash paid for income taxes	6,088		15,791
Cash paid for interest	5,777		7,521
SUPPLEMENTAL CASH FLOW DISCLOSURES FOR NON-CASH INVESTING AND FINANCING ACTIVITIES:
Decrease in accounts payable and accrued liabilities related to fixed assets	$ (5,801)		$ (7,678)
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

NATURE OF OPERATIONS

NATURE OF OPERATIONS	9 Months Ended
	Sep. 30, 2019
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, 2019
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, 2018 included in the Company’s Annual Report on Form 10-K. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2019 or any other period. On January 1, 2019, the Company adopted Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 842, Leases (ASC Topic 842) using the modified retrospective method for all lease arrangements at the beginning of the period of adoption. Results for reporting periods beginning January 1, 2019 are presented under ASC Topic 842, while prior period amounts were not adjusted and continue to be presented in accordance with the Company’s historical accounting under ASC Topic 840, Leases . ASC Topic 842 had a material impact on the Company’s Condensed Consolidated Balance Sheet but did not have a significant impact on the Company’s consolidated net loss. The Company elected to use the practical expedient allowing the use-of-hindsight and reassessed the lease term for all unexpired leases that commenced before the effective date of ASC Topic 842. For leases that commenced and expired before the effective date of ASC Topic 842, the Company elected not to reassess the expired leases. The Company also elected not to include leases with initial terms of twelve months or less in the recognized right-of-use (ROU) assets and lease liabilities. As a result of the cumulative impact of adopting ASC Topic 842, the Company recorded lease ROU assets of $55.9 million and lease liabilities of $59.0 million as of January 1, 2019, primarily related to real estate and equipment, based on the present value of future lease payments on the date of adoption. The difference between the ROU assets and lease liabilities was recorded as an adjustment to Accumulated Deficit. Refer to Note 11 for additional disclosures required by ASC Topic 842. On January 1, 2019, the Company adopted Accounting Standards Update No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12), using the modified retrospective method. This ASU provides new guidance about income statement classification and eliminates the requirement to separately measure and report hedge ineffectiveness. Results for reporting periods beginning January 1, 2019 are presented under ASU 2017-12, while prior period amounts were not adjusted and continue to be presented in accordance with the Company’s historical accounting. The adoption of this ASU did not have a material impact on the Company’s Condensed Consolidated Financial Statements. See Note 10 for additional disclosures required by ASU 2017-12. 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. 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 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, 2019
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Except as detailed below, there have been no material changes to the Company’s significant accounting policies during the nine months ended September 30, 2019 , 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, 2018 . Leases The Company determines if an arrangement is a lease at inception. For leases where the Company is the lessee, ROU assets represent the Company’s right to use the underlying asset for the term of the lease and the lease liabilities represent an obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of the future lease payments over the lease term. The Company uses its incremental borrowing rate based on the information available at the commencement date of the underlying lease arrangement to determine the present value of lease payments. The ROU asset also includes any prepaid lease payments and any lease incentives received. The lease term to calculate the ROU asset and related lease liability includes options to extend or terminate the lease when it is reasonably certain that the Company will exercise the option. The Company’s lease agreements generally do not contain any material variable lease payments, residual value guarantees or restrictive covenants. Lease expense for operating leases is recognized on a straight-line basis over the lease term as an operating expense while expense for financing leases is recognized as depreciation expense and interest expense using the accelerated interest method of recognition. When an arrangement requires payments for lease and non-lease components, the Company has elected to account for lease and non-lease components separately. Lease expense for leases with a term of twelve months or less is recognized on a straight-line basis. Derivatives and Hedging Activities The Company accounts for its derivative instruments as either assets or liabilities on the balance sheet and measures them at fair value, which is estimated using current exchange rates and interest rates and takes into consideration the current creditworthiness of the counterparties or the Company, as applicable. For derivatives designated as hedging instruments, the entire change in the fair value of qualifying derivative instruments is recorded in Accumulated Other Comprehensive Income (AOCI) and amounts deferred in AOCI will be reclassified to earnings in the same line item in which the earnings effect of the hedged item is reported. Derivatives not designated as hedging instruments are adjusted to fair value through earnings in Operating Expenses in the Consolidated Statements of Comprehensive Income (Loss).

RECENT ACCOUNTING PRONOUNCEMENT

RECENT ACCOUNTING PRONOUNCEMENTS	9 Months Ended
	Sep. 30, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS Except as described in Note 2 – Basis of Presentation and below, 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, 2019 , 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, 2018 , that the Company believes are of significance or potential significance to the Company. Accounting Pronouncements Not Yet Adopted Effective January 1, 2020, the Company will adopt 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, with certain exceptions allowed. The standard amends 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. The Company is evaluating the impact of the adoption of ASU 2016-13 on its Condensed Consolidated Financial Statements.

FINANCIAL INSTRUMENTS

FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
FINANCIAL INSTRUMENTS	FINANCIAL INSTRUMENTS All marketable securities were classified as available-for-sale at September 30, 2019 and December 31, 2018 . The following tables show the Company’s cash, cash equivalents and available-for-sale securities by significant investment category as of September 30, 2019 and December 31, 2018 , respectively: As of September 30, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Aggregate Fair Value Cash and Cash Equivalents Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash $ 294,543 $ — $ — $ 294,543 $ 294,543 $ — $ — Level 2: Money market instruments 128,678 — — 128,678 128,678 — — Corporate debt securities 519,693 3,713 (67 ) 523,339 — 206,782 316,557 U.S. government agency securities 204,371 1,073 (97 ) 205,347 — 90,790 114,557 Foreign and other 549 142 (1 ) 690 — — 690 Subtotal 853,291 4,928 (165 ) 858,054 128,678 297,572 431,804 Total $ 1,147,834 $ 4,928 $ (165 ) $ 1,152,596 $ 423,220 $ 297,572 $ 431,804 As of December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Aggregate Fair Value Cash and Cash Equivalents Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash $ 228,809 $ — $ — $ 228,809 $ 228,809 $ — $ — Level 2: Money market instruments 205,736 — — 205,736 205,736 — — Corporate debt securities 564,852 214 (2,288 ) 562,778 2,000 376,545 184,233 Commercial paper 77,702 — — 77,702 21,964 55,738 — U.S. government agency securities 240,436 144 (697 ) 239,883 31,474 156,967 51,442 Foreign and other 5,126 139 (1 ) 5,264 3,999 1,076 189 Subtotal 1,093,852 497 (2,986 ) 1,091,363 265,173 590,326 235,864 Total $ 1,322,661 $ 497 $ (2,986 ) $ 1,320,172 $ 493,982 $ 590,326 $ 235,864 (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 and five years. As of September 30, 2019 , the Company’s investments in an unrealized loss position were not significant, and since the Company has the ability and intent to hold all investments that have been in a continuous loss position until maturity or recovery, no other-than-temporary impairment was deemed to have occurred.

INTANGIBLE ASSETS

INTANGIBLE ASSETS	9 Months Ended
	Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	INTANGIBLE ASSETS Intangible assets consisted of the following: September 30, December 31, Intangible assets: Finite-lived intangible assets $ 642,677 $ 307,995 Indefinite-lived intangible assets — 326,359 Gross intangible assets: 642,677 634,354 Less: Accumulated amortization (179,828 ) (142,546 ) Net carrying value $ 462,849 $ 491,808 During the second quarter of 2019, $326.4 million of indefinite-lived intangible assets were reclassified to definite-lived as the underlying in-process research and development (IPR&D) was placed into service upon receiving European regulatory approval for Palynziq. The Company will straight-line the amortization expense for the underlying IPR&D over its estimated useful life through August 2028. During the second quarter of 2019, the Company recorded a $15.0 million gain on sale of intangible assets in the Condensed 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, 2019
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	(7) PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment, net consisted of the following: September 30, December 31, Building and improvements $ 709,990 $ 694,447 Manufacturing and laboratory equipment 365,348 345,947 Computer hardware and software 165,235 157,787 Leasehold improvements 52,379 41,188 Furniture and equipment 37,603 33,234 Land improvements 7,239 6,551 Land 83,094 77,993 Construction-in-progress 84,021 64,170 1,504,909 1,421,317 Accumulated depreciation (535,609 ) (472,635 ) Total property, plant and equipment, net $ 969,300 $ 948,682 The construction-in-progress balance primarily included costs related to significant in-process projects at the Company's facilities in Marin County, California, and Shanbally, Ireland. Depreciation expense for the three and nine months ended September 30, 2019 was $24.2 million and $67.2 million , respectively, of which $9.8 million and $24.9 million , respectively, was capitalized into inventory. Depreciation expense for the three and nine months ended September 30, 2018 was $26.6 million and $66.7 million , respectively, of which $8.1 million and $18.6 million , respectively, was capitalized into inventory.

SUPPLEMENTAL BALANCE SHEET INFO

SUPPLEMENTAL BALANCE SHEET INFORMATION	9 Months Ended
	Sep. 30, 2019
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 $ 68,391 $ 74,616 Work-in-process 321,073 231,064 Finished goods 219,585 225,191 Total inventory $ 609,049 $ 530,871 Inventory as of September 30, 2019 , included manufacturing-related costs for the commercial production of valoctocogene roxaparvovec inventory totaling $7.1 million . 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. The Company believes that all material uncertainties related to the ultimate regulatory approval of valoctocogene roxaparvovec for commercial sale have been significantly reduced. A number of factors were taken into consideration, including the current 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 regulatory approval is not obtained, the manufacturing-related costs for the commercial production of valoctocogene roxaparvovec will be expensed. Accounts Payable and Accrued Liabilities consisted of the following: September 30, 2019 December 31, 2018 Accounts payable and accrued operating expenses $ 226,769 $ 207,620 Accrued compensation expense 132,049 149,937 Accrued rebates payable 55,957 43,116 Accrued royalties payable 27,881 19,977 Value added taxes payable 7,556 7,785 Forward foreign currency exchange contracts 8,731 4,178 Lease liability 10,225 — Other 14,577 4,677 Total accounts payable and accrued liabilities $ 483,745 $ 437,290

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	9 Months Ended
	Sep. 30, 2019
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, 2018 . 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, 2019 and December 31, 2018 . 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, 2019 . Fair Value Measurements at September 30, 2019 Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets: Other current assets: NQDC Plan assets $ 1,135 $ — $ 1,135 Other assets: NQDC Plan assets 15,039 — 15,039 Restricted investments (1) 3,157 — 3,157 Total other assets 18,196 — 18,196 Total assets $ 19,331 $ — $ 19,331 Liabilities: Current liabilities: NQDC Plan liability (2) $ 1,135 $ — $ 1,135 Contingent consideration — 10,000 10,000 Total current liabilities 1,135 10,000 11,135 Other long-term liabilities: NQDC Plan liability (2) 15,039 — 15,039 Contingent consideration — 48,930 48,930 Total other long-term liabilities 15,039 48,930 63,969 Total liabilities $ 16,174 $ 58,930 $ 75,104 Fair Value Measurements at December 31, 2018 Quoted Price in Active Markets For Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets: Other current assets: NQDC Plan assets $ — $ 370 $ — $ 370 Restricted investments (1) — 9,581 — 9,581 Total other current assets — 9,951 — 9,951 Other assets: NQDC Plan assets — 12,828 — 12,828 Restricted investments (1) — 2,450 — 2,450 Strategic investments (3) 942 — — 942 Total other assets 942 15,278 — 16,220 Total assets $ 942 $ 25,229 $ — $ 26,171 Liabilities: Current liabilities: NQDC Plan liability $ 55 $ 370 $ — $ 425 Contingent consideration — — 85,951 85,951 Total current liabilities 55 370 85,951 86,376 Other long-term liabilities: NQDC Plan liability 17,598 12,828 — 30,426 Contingent consideration — — 46,883 46,883 Total other long-term liabilities 17,598 12,828 46,883 77,309 Total liabilities $ 17,653 $ 13,198 $ 132,834 $ 163,685 (1) The restricted investments at September 30, 2019 and December 31, 2018 secure the Company's irrevocable standby letters of credit obtained in connection with certain commercial agreements. (2) The Company’s NQDC Plan was amended during the second quarter of 2019, which resulted in a change to the classification of the obligation associated with the Company's common stock held in the NQDC Plan. The obligation was previously classified as a liability recorded at fair value and has been reclassified into equity and recorded at the shares' respective grant date fair values at June 30, 2019. The change to the NQDC Plan related to the prohibition of participants to diversify investments for deferrals of Company stock contributed into other types of investments. The NQDC Plan liabilities classified as Level 2 represent investments held in plan assets excluding shares of the Company's common stock. (3) The Company had investments in marketable equity securities measured using quoted prices in an active market that were considered strategic investments and were included in Other Assets on the Company's Condensed Consolidated Balance Sheets. During the second quarter of 2019, the Company realized an immaterial gain upon the sale of the shares. There were no transfers between levels during the three and nine months ended September 30, 2019 . The following table represents a roll-forward of contingent consideration. Contingent consideration at December 31, 2018 $ 132,834 Changes in fair value of other contingent consideration 19,916 Milestone payments to Ares Trading S.A. (Merck Serono) (83,472 ) Milestone payments to former LEAD Therapeutics, Inc. shareholders (5,987 ) Realized gain on settlement of contingent consideration (1,928 ) Foreign exchange remeasurement of Euro denominated contingent consideration (2,433 ) Contingent consideration at September 30, 2019 $ 58,930

DERIVATIVE INSTRUMENTS AND HEDG

DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES	9 Months Ended
	Sep. 30, 2019
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 product revenues and operating expenses being denominated in currencies other than the U.S. Dollar (USD), primarily the Euro. The Company designates certain of these forward contracts as hedging instruments and also uses forward contracts for economic hedging purposes which are not designated as hedging instruments. Whether designated or undesignated, these forward contracts protect against the reduction in value of forecasted foreign currency cash flows resulting from net product revenues, operating expenses and asset or liability positions designated in currencies other than the USD. To receive hedge accounting treatment, derivatives that hedge cash flows must be highly effective at 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 following table summarizes the Company’s derivatives designated as hedging instruments outstanding as of September 30, 2019 (notional amounts in millions): Foreign Exchange Contracts Number of Contracts Aggregate Notional Amount in Foreign Currency Maturity Australian Dollars – Sell 6 2.8 Oct 2019 - Dec 2019 Canadian Dollars – Sell 24 28.1 Oct 2019 - Sept 2020 Colombian Pesos – Sell 12 89,400.0 Oct 2019 - Sept 2020 Euros – Purchase 150 189.4 Oct 2019 - Sept 2022 Euros – Sell 453 624.2 Oct 2019 - Sept 2022 Norwegian Krone – Sell 3 11.7 Oct 2019 - Dec 2019 Total 648 The following table summarizes the Company’s derivatives not designated as hedging instruments outstanding as of September 30, 2019 (notional amounts in millions): Foreign Exchange Contracts Number of Contracts Aggregate Notional Amount in Foreign Currency Maturity Colombian Pesos – Sell 2 96,000.0 Oct 2019 - Nov 2019 Euros – Purchase 2 44.1 Oct 2019 - Nov 2019 Great British Pounds - Purchase 1 4.9 Oct 2019 Great British Pounds - Sell 1 2.0 Oct 2019 Rubles – Sell 2 1,420.0 Oct 2019 - Nov 2019 Total 8 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, 2019 December 31, 2018 Derivatives designated as hedging instruments: Asset Derivatives - Level 2 (1) Other current assets $ 29,900 $ 12,686 Other assets 22,892 10,324 Subtotal $ 52,792 $ 23,010 Liability Derivatives - Level 2 (1) Accounts payable and accrued liabilities $ 7,875 $ 4,036 Other long-term liabilities 7,641 3,653 Subtotal $ 15,516 $ 7,689 Derivatives not designated as hedging instruments: Asset Derivatives - Level 2 (1) Other current assets $ 71 $ 168 Other assets — — Subtotal $ 71 $ 168 Liability Derivatives - Level 2 (1) Accounts payable and accrued liabilities $ 858 $ 142 Other long-term liabilities — — Subtotal $ 858 $ 142 Total Derivatives Assets $ 52,863 $ 23,178 Total Derivatives Liabilities $ 16,374 $ 7,831 (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, 2018 . The following tables summarize the impact of gains and losses from the Company's derivatives on its Condensed Consolidated Financial Statements for the period presented. Three Months Ended Nine Months Ended Derivatives Designated as Cash Flow Hedging Instruments September 30, 2019 September 30, 2019 Amount of Gain (Loss) Recognized in Other Comprehensive Income $ 23,973 $ 35,431 Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Derivatives Designated as Cash Flow Hedging Instruments Cash Flow Hedging Gains (Losses) Reclassified into Earnings Cash Flow Hedging Gains (Losses) Net product revenues as reported $ 450,900 $ 6,196 $ 1,224,458 $ 11,171 Operating expenses as reported $ 457,087 $ (1,388 ) $ 1,340,900 $ (1,885 ) Derivatives Not Designated as Hedging Instruments Gains (Losses) Recognized in Earnings Gains (Losses) Recognized in Earnings Operating Expenses $ (1,286 ) $ (5,182 ) As of September 30, 2019 , the Company expects to reclassify unrealized gains of $19.2 million from AOCI to earnings as the forecasted revenue and operating expense transactions occur over the next 12 months. 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.

LEASES

LEASES	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
LEASES	LEASES The following table presents the Company’s right-of-use (ROU) assets and lease liabilities as of September 30, 2019 : Lease Classification Classification September 30, Assets: Operating Other Assets $ 51,284 Financing Other Assets 10,346 Total ROU assets $ 61,630 Liabilities: Current: Operating Accounts payable and accrued liabilities $ 7,273 Financing Accounts payable and accrued liabilities 2,952 Noncurrent: Operating Other long-term liabilities 45,499 Financing Other long-term liabilities 9,544 Total lease liabilities $ 65,268 Maturities of lease liabilities as of September 30, 2019 by fiscal year were as follows: Maturity of Lease Liabilities Operating Financing Total Remainder of 2019 $ 3,115 $ 3,204 $ 6,319 2020 9,925 3,464 13,389 2021 8,721 2,865 11,586 2022 8,406 2,258 10,664 2023 7,504 1,748 9,252 Thereafter 27,464 — 27,464 Total lease payments 65,135 13,539 78,674 Less: Interest (12,363 ) (1,043 ) (13,406 ) Present value of lease liabilities $ 52,772 $ 12,496 $ 65,268 Lease Cost Classification Three Months Ended Nine Months Ended Operating (1) Operating Expenses $ 3,535 $ 9,946 Financing: Amortization Operating Expenses 600 1,811 Interest expense Operating Expenses 142 455 Total lease costs $ 4,277 $ 12,212 (1) Includes short-term leases and variable lease costs, both of which were not material. Other Information September 30, Weighted average remaining lease term (in years): Operating leases 8.0 Financing leases 4.2 Weighted average discount rate: Operating leases 5.2 % Financing leases 5.4 % As of September 30, 2019 , no operating leases are expected to commence in the remainder of 2019. Supplemental Cash Flow Information Nine Months Ended Cash paid for amounts included in the measurement of lease liabilities: Cash used in operating activities: Operating leases $ 5,918 Financing leases $ 454 Cash used in financing activities: Financing leases $ 2,027 ROU assets obtained in exchange for lease obligations: Operating leases $ 9,268 Financing leases $ 72 Lease Commitments as of December 31, 2018 Minimum lease payments for future years as of December 31, 2018 were as follows: 2019 $ 12,976 2020 12,549 2021 11,198 2022 10,574 2023 9,993 Thereafter 27,701 Total $ 84,991 Rent expense for the year ended December 31, 2018 was $12.2 million . Total deferred rent accruals at December 31, 2018 were $2.1 million , of which $0.5 million was short-term.

DEBT

DEBT	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
DEBT	DEBT Convertible Notes As of September 30, 2019 , the Company had outstanding fixed-rate notes with varying maturities for an undiscounted aggregate principal amount of $870.0 million (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, 1.50% senior subordinated convertible notes due in October 2020 (the 2020 Notes) 374,993 374,993 Unamortized discount (15,780 ) (26,581 ) Unamortized deferred offering costs (1,359 ) (2,334 ) Convertible Notes due in 2020, net 357,854 346,078 0.599% senior subordinated convertible notes due in August 2024 (the 2024 Notes) 495,000 495,000 Unamortized discount (6,887 ) (7,946 ) Unamortized deferred offering costs (2,351 ) (2,715 ) Convertible Notes due in 2024, net 485,762 484,339 Total convertible debt, net $ 843,616 $ 830,417 Fair value of fixed rate convertible debt Convertible Notes due in October 2020 (1) 384,713 419,722 Convertible Notes due in August 2024 (1) 490,297 491,626 Total fair value of fixed rate convertible debt $ 875,010 $ 911,348 (1) 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, 2018 . Interest expense on the Company’s convertible debt consisted of the following: Three Months Ended September 30, Nine Months Ended 2019 2018 2019 2018 Coupon interest expense $ 2,271 $ 3,331 $ 6,681 $ 9,819 Amortization of debt issuance costs 508 1,008 1,522 3,018 Accretion of discount on convertible notes 4,005 7,792 11,860 23,081 Total interest expense on convertible debt $ 6,784 $ 12,131 $ 20,063 $ 35,918 See Note 12 to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 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 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 range from 0.15% to 0.35% per annum based upon the Company’s net leverage ratio and EBITDA for each of the two most recently ended four-quarter measurement periods. The Company’s obligations under the Credit Facility are guaranteed by its direct subsidiary, California Corporate Center Acquisition LLC, and such obligations may in the future be guaranteed from time to time by certain other material domestic subsidiaries. The 2018 Credit Facility matures on October 19, 2021 at which time all outstanding amounts become due and payable, except that if at least $100.0 million aggregate principal amount of the 2020 Notes remain outstanding on August 1, 2020 and certain other conditions have not been met, the Company may be required to repay all amounts borrowed under the 2018 Credit Facility on August 1, 2020 . The Company incurred approximately $1.0 million of issuance costs, which will be amortized to Interest Expense over the term of the 2018 Credit Facility. The 2018 Credit Facility contains financial covenants requiring the Company to maintain a minimum interest coverage ratio and a minimum liquidity requirement. As of September 30, 2019 , and December 31, 2018 , there were no outstanding amounts due on nor any usage of the 2018 Credit Facility. As of September 30, 2019 , the Company and certain of its subsidiaries that served as guarantors were in compliance with all covenants.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME	9 Months Ended
	Sep. 30, 2019
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, 2019 and 2018 . Three Months Ended Nine Months Ended Condensed Consolidated Statement of Comprehensive Income (Loss) Classification 2019 2018 2019 2018 Gains (losses) on cash flow hedges: Forward contracts $ 6,196 $ 5,025 $ 11,171 $ (6,683 ) Net product revenues Forward contracts (1,388 ) 498 (1,885 ) 3,762 Operating expenses Total gain (loss) on cash flow hedges $ 4,808 $ 5,523 $ 9,286 $ (2,921 ) 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, 2019 and 2018 . Three Months Ended September 30, 2019 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Available for-Sale Debt Securities Other Total AOCI balance at June 30, 2019 $ 14,181 $ 3,271 $ (13 ) $ 17,439 Other comprehensive income (loss) before reclassifications 23,973 522 (3 ) 24,492 Less: net 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, 2019 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Available for-Sale Debt Securities Other Total AOCI balance at December 31, 2018 $ 7,201 $ (1,917 ) $ (13 ) $ 5,271 Other comprehensive income (loss) before reclassifications 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 Three Months Ended September 30, 2018 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Available for-Sale Debt Securities Other Total AOCI balance at June 30, 2018 $ 2,568 $ (3,686 ) $ (11 ) $ (1,129 ) Other comprehensive income (loss) before 3,355 1,475 — 4,830 Less: gain (loss) reclassified from AOCI 5,523 — — 5,523 Tax effect — (338 ) — (338 ) Net current-period other comprehensive income (loss) (2,168 ) 1,137 — (1,031 ) AOCI balance at September 30, 2018 $ 400 $ (2,549 ) $ (11 ) $ (2,160 ) Nine Months Ended September 30, 2018 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Available for-Sale Debt Securities Other Total AOCI balance at December 31, 2017 $ (20,232 ) $ (2,722 ) $ (7 ) $ (22,961 ) Impact of change in accounting principle — (586 ) — (586 ) AOCI balance at January 1, 2018 $ (20,232 ) $ (3,308 ) $ (7 ) $ (23,547 ) Other comprehensive income (loss) before 17,711 985 (4 ) 18,692 Less: gain (loss) reclassified from AOCI (2,921 ) — — (2,921 ) Tax effect — (226 ) — (226 ) Net current-period other comprehensive income (loss) 20,632 759 (4 ) 21,387 AOCI balance at September 30, 2018 $ 400 $ (2,549 ) $ (11 ) $ (2,160 )

REVENUE, CREDIT CONCENTRATIONS

REVENUE, CREDIT CONCENTRATIONS AND GEOGRAPHIC INFORMATION	9 Months Ended
	Sep. 30, 2019
Concentration Risk And Geographic Information [Abstract]
REVENUE, CREDIT CONCENTRATIONS AND GEOGRAPHIC INFORMATION	REVENUE, CREDIT CONCENTRATIONS AND GEOGRAPHIC INFORMATION The 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. Although Sanofi Genzyme (Genzyme) sells Aldurazyme worldwide, the 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. Genzyme is the Company’s sole customer for Aldurazyme and is responsible for marketing and selling Aldurazyme to third parties. Three Months Ended Nine Months Ended 2019 2018 2019 2018 Total revenues by geographic region: United States $ 201,874 $ 174,722 $ 562,217 $ 528,082 Europe 125,485 111,069 369,585 323,940 Latin America 83,799 75,400 164,132 151,955 Rest of world 49,939 30,515 153,671 134,021 Total revenues $ 461,097 $ 391,706 $ 1,249,605 $ 1,137,998 The following table disaggregates Net Product Revenues by product. Three Months Ended Nine Months Ended 2019 2018 2019 2018 Net product revenues by product: Aldurazyme $ 22,852 $ 27,593 $ 73,945 $ 117,652 Brineura 19,840 9,936 46,815 27,743 Firdapse 5,668 4,977 16,262 15,080 Kuvan 120,524 113,254 340,771 321,414 Naglazyme 94,408 103,089 279,462 269,171 Palynziq 24,142 4,129 55,250 4,129 Vimizim 163,466 123,342 411,953 368,016 Total net product revenues $ 450,900 $ 386,320 $ 1,224,458 $ 1,123,205 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, the Company’s sole customer for Aldurazyme. Three Months Ended Nine Months Ended 2019 2018 2019 2018 United States $ 175,127 $ 146,742 $ 480,330 $ 409,294 Europe 121,363 107,851 358,041 315,270 Latin America 83,799 75,400 164,132 151,955 Rest of world 47,759 28,734 148,010 129,034 Total net product revenues marketed by the Company 428,048 358,727 1,150,513 1,005,553 Aldurazyme net product revenues marketed by Genzyme 22,852 27,593 73,945 117,652 Total net product revenues $ 450,900 $ 386,320 $ 1,224,458 $ 1,123,205 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 2019 2018 2019 2018 Customer A 16 % 16 % 17 % 17 % Customer B 13 % 12 % 12 % 12 % Customer C 10 % 10 % 11 % 10 % Customer D 5 % 7 % 6 % 11 % Customer E 12 % — % 6 % — % Customer F — % 13 % — % 6 % Total 56 % 58 % 52 % 56 % On a consolidated basis, three customers accounted for 23% , 14% and 12% of the September 30, 2019 accounts receivable balance, respectively, compared to December 31, 2018 , when two customers accounted for 30% and 16% of the accounts receivable balance, respectively. As of September 30, 2019 , and December 31, 2018 , the accounts receivable balance for Genzyme included $67.7 million and $73.9 million , respectively, of unbilled accounts receivable, which become 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 immediate payment in certain circumstances. The Company sells its products in countries that face economic volatility and weakness. Although the Company has historically collected receivables from customers in such countries, sustained weakness or further deterioration of the local economies and currencies may cause customers in those countries to be unable to pay for the Company’s products. The Company has not historically experienced a significant level of uncollected receivables and has received continued payments from its more aged accounts in these countries. The Company believes that the allowances for doubtful accounts related to these countries, if any, is adequate based on its analysis of the specific business circumstances and expectations of collection for each of the underlying accounts in these countries.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION 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 September 30, Nine Months Ended 2019 2018 2019 2018 Cost of sales $ 4,093 $ 3,974 $ 12,629 $ 10,360 Research and development 14,261 14,257 43,037 43,099 Selling, general and administrative 20,819 18,815 66,097 58,802 Total stock-based compensation expense $ 39,173 $ 37,046 $ 121,763 $ 112,261 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, compared to $5.3 million and $14.3 million for the three and nine months ended September 30, 2018 , respectively. Capitalized stock-based compensation is recognized as cost of sales when the related product is sold. Equity Awards with Service-Based Vesting Conditions During the nine months ended September 30, 2019 , the Company granted 1,844,308 RSUs with service-based vesting conditions with a weighted-average fair value of $91.23 per share. The Company did no t grant any options to purchase shares of common stock during the three months ended September 30, 2019 . During the nine months ended September 30, 2019 , the Company granted 610,250 options to purchase shares of common stock with a weighted-average fair value of $36.84 per share. The assumptions used to estimate the per share fair value of stock options granted during the periods presented were as follows: Three Months Ended Nine Months Ended 2019 2018 2019 2018 Expected volatility N/A 36.8% 37.1 – 37.4% 36.8 – 38.4% Dividend yield N/A 0.0% 0.0% 0.0% Expected life (in years) N/A 5.7 4.6 – 5.8 4.6 – 5.7 Risk-free interest rate N/A 2.8% 2.2 – 3.0% 2.3 – 2.8% The Company did not issue any new stock purchase rights under the Employee Stock Purchase Plan during the three months ended September 30, 2019 . The Company issued 107,473 new stock purchase rights under the Employee Stock Purchase Plan during the nine months ended September 30, 2019 . Restricted Stock Unit Awards with Performance Conditions In August 2019, the Compensation Committee of the Board of Directors (Board) approved the grant of 44,260 RSUs with performance-based vesting conditions and a grant date fair value of $ 81.00 per RSU. This award is contingent upon obtaining regulatory approval for valoctocogene roxaparvovec by January 2022 and the awarded RSUs, if any, vest ratably from the time regulatory approval is obtained through January 2022. The Company evaluated the current timeline and plans for submitting the regulatory applications and determined that for accounting purposes attainment of the performance measure is not probable as of September 30, 2019 as the regulatory approval is outside of the Company's control. Therefore, the Company did not record any expense associated with these awards. In March 2019, the Compensation Committee and Board approved the grant of 99,010 RSUs with performance-based vesting conditions (base RSUs) and a grant date fair value of $94.53 per RSU. This award is contingent upon the achievement of a 2019 revenue target and the awarded RSUs, if any, vest ratably over a three -year service period. The Company evaluated the 2019 revenue target in the context of its current 2019 revenue forecast, and related confidence level in the forecast, and determined that attainment of the revenue target was probable for accounting purposes commencing in the first quarter of 2019 . The number of shares that may be earned range between 0% and 200% of the base RSUs, depending on the percentage of 2019 “managed revenues” (defined as the Company’s net product revenues, excluding net revenues attributable to Aldurazyme, and determined using fixed foreign currency exchange rates) achieved against the target managed revenues, with a threshold achievement level of 75% of target and a ceiling achievement level of 125% of target. Restricted Stock Unit Awards with Market Conditions In March 2019, the Compensation Committee and Board approved the grant of 99,010 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 50 th 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 $143.92 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.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company utilizes an estimated annual effective tax rate for calculating a tax provision under ASC 740-270. That rate is applied to year-to-date ordinary income or loss in order to compute the year-to-date income tax provision. For the three months ended September 30, 2019 , the Company recognized a net tax benefit of $45.2 million primarily attributed to the quarter fluctuations in the mix and timing of our profits and losses on a territorial basis when applying the estimated annual effective tax rate to the year-to-date earnings. The Company utilizes the asset and liability method of accounting for income taxes. Under this method, deferred taxes are determined based on the difference between the financial statement and tax bases of assets and liabilities using tax rates expected to be in effect in the years in which the differences are expected to reverse. A valuation allowance is recorded to reduce deferred tax assets to the amount that is more likely than not to be realized. The Company’s Dutch subsidiary had a full valuation allowance against a deferred tax asset of $29.6 million at December 31, 2018. Historical earnings, future taxable income and ongoing prudent and feasible tax planning strategies have been considered in assessing the need for the valuation allowance; and based on projected income and other key operating factors, the Company concluded in the second quarter of 2019 that it is more likely than not that the benefit of these deferred tax assets would be realized. As a result, the amount of the valuation allowance related to the deferred tax assets that are expected to be realized was reversed in the second quarter of 2019, resulting in a net tax benefit of $27.1 million

NET LOSS PER COMMON SHARE

NET LOSS PER COMMON SHARE	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
NET 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 ESPP, unvested RSUs, common stock held by the Company's NQDC Plan and contingent issuances of common stock related to convertible debt. The following table sets forth the computation of basic and diluted earnings per common share (in thousands of common shares): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Numerator: Net Income (Loss), basic $ 55,036 $ (12,620 ) $ (38,872 ) $ (73,561 ) Add: Interest on 2024 notes 937 — — — Net Income (Loss), diluted $ 55,973 $ (12,620 ) $ (38,872 ) $ (73,561 ) Denominator: Weighted-average common shares outstanding, basic 179,289 177,481 178,873 176,767 Effect of dilutive securities: Options to purchase common stock 1,560 — — — Common stock issuable under the 2024 notes 3,970 — — — Unvested RSUs 669 — — — Common stock potentially issuable for ESPP purchases 231 — — — Common shares held by the NQDC 205 — — — Weighted-average common shares outstanding, diluted 185,924 177,481 178,873 176,767 Net Income (Loss) per common share, basic 0.31 (0.07 ) (0.22 ) (0.42 ) Net Income (Loss) per common share, diluted 0.30 (0.07 ) (0.22 ) (0.42 ) 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 using the if-converted or treasury stock method (in thousands of common shares): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Options to purchase common stock 5,829 7,517 7,388 7,517 Common stock issuable under the 2018 Notes — 3,983 — 3,983 Common stock issuable under the 2020 Notes 3,983 3,983 3,983 3,983 Common stock issuable under the 2024 Notes — 3,970 3,970 3,970 Unvested RSUs 3,360 3,411 4,029 3,411 Common stock potentially issuable for ESPP purchases 222 407 453 407 Common stock held by the NQDC — 208 205 208 Total number of potentially issuable shares 13,394 23,479 20,028 23,479 The potential effect of the capped call transactions with respect to the 2020 Notes was excluded from the diluted net loss per share as of September 30, 2019 as the Company’s closing stock price on September 30, 2019 did not exceed the conversion price of $94.15 per share. Although the Company’s stock price on September 28, 2018 (the last trading day before September 30, 2018) exceeded the conversion price, the potential effect of the capped call transactions and potential shares issuable under the Company’s 0.75% senior subordinated convertible notes due in 2018 and the 2020 Notes were excluded from the calculation of diluted loss per share in the three and nine months ended September 30, 2018 as they were anti-dilutive using the if-converted method. There is no similar capped call transaction associated with the 2024 Notes. See Note 12 to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 for additional information related to the Company’s convertible debt and capped call transaction.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2019
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 and 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, 2019 , the Company was subject to contingent payments totaling approximately $376.9 million upon achievement of certain development and regulatory activities and commercial sales and licensing milestones if they occur before certain dates in the future. Of this amount, $65.5 million relates to the acquisition of certain rights and other assets with respect to Kuvan and Palynziq from a third party and $239.7 million relates to programs that are no longer being developed. As of September 30, 2019 , the Company recorded a total of $69.1 million of contingent liabilities, of which $ 20.2 million was short-term. See Note 9 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 and certain other inventory-related items. As of September 30, 2019 , such commitments and other minimum contractual obligations for clinical and post-marketing services were estimated at approximately $131.6 million .

BASIS OF PRESENTATION (Policies

BASIS OF PRESENTATION (Policies)	9 Months Ended
	Sep. 30, 2019
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, 2018 included in the Company’s Annual Report on Form 10-K. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2019 or any other period. On January 1, 2019, the Company adopted Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 842, Leases (ASC Topic 842) using the modified retrospective method for all lease arrangements at the beginning of the period of adoption. Results for reporting periods beginning January 1, 2019 are presented under ASC Topic 842, while prior period amounts were not adjusted and continue to be presented in accordance with the Company’s historical accounting under ASC Topic 840, Leases . ASC Topic 842 had a material impact on the Company’s Condensed Consolidated Balance Sheet but did not have a significant impact on the Company’s consolidated net loss. The Company elected to use the practical expedient allowing the use-of-hindsight and reassessed the lease term for all unexpired leases that commenced before the effective date of ASC Topic 842. For leases that commenced and expired before the effective date of ASC Topic 842, the Company elected not to reassess the expired leases. The Company also elected not to include leases with initial terms of twelve months or less in the recognized right-of-use (ROU) assets and lease liabilities. As a result of the cumulative impact of adopting ASC Topic 842, the Company recorded lease ROU assets of $55.9 million and lease liabilities of $59.0 million as of January 1, 2019, primarily related to real estate and equipment, based on the present value of future lease payments on the date of adoption. The difference between the ROU assets and lease liabilities was recorded as an adjustment to Accumulated Deficit. Refer to Note 11 for additional disclosures required by ASC Topic 842. On January 1, 2019, the Company adopted Accounting Standards Update No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12), using the modified retrospective method. This ASU provides new guidance about income statement classification and eliminates the requirement to separately measure and report hedge ineffectiveness. Results for reporting periods beginning January 1, 2019 are presented under ASU 2017-12, while prior period amounts were not adjusted and continue to be presented in accordance with the Company’s historical accounting. The adoption of this ASU did not have a material impact on the Company’s Condensed Consolidated Financial Statements. See Note 10 for additional disclosures required by ASU 2017-12. 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. 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 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.
Leases	Leases The Company determines if an arrangement is a lease at inception. For leases where the Company is the lessee, ROU assets represent the Company’s right to use the underlying asset for the term of the lease and the lease liabilities represent an obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of the future lease payments over the lease term. The Company uses its incremental borrowing rate based on the information available at the commencement date of the underlying lease arrangement to determine the present value of lease payments. The ROU asset also includes any prepaid lease payments and any lease incentives received. The lease term to calculate the ROU asset and related lease liability includes options to extend or terminate the lease when it is reasonably certain that the Company will exercise the option. The Company’s lease agreements generally do not contain any material variable lease payments, residual value guarantees or restrictive covenants.
Derivatives and Hedging Activities	Derivatives and Hedging Activities The Company accounts for its derivative instruments as either assets or liabilities on the balance sheet and measures them at fair value, which is estimated using current exchange rates and interest rates and takes into consideration the current creditworthiness of the counterparties or the Company, as applicable. For derivatives designated as hedging instruments, the entire change in the fair value of qualifying derivative instruments is recorded in Accumulated Other Comprehensive Income (AOCI) and amounts deferred in AOCI will be reclassified to earnings in the same line item in which the earnings effect of the hedged item is reported. Derivatives not designated as hedging instruments are adjusted to fair value through earnings in Operating Expenses in the Consolidated Statements of Comprehensive Income (Loss).
New Accounting Pronouncements	Accounting Pronouncements Not Yet Adopted Effective January 1, 2020, the Company will adopt 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, with certain exceptions allowed. The standard amends 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. The Company is evaluating the impact of the adoption of ASU 2016-13 on its Condensed Consolidated Financial Statements.

FINANCIAL INSTRUMENTS (Tables)

FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2019
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 as of September 30, 2019 and December 31, 2018 , respectively: As of September 30, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Aggregate Fair Value Cash and Cash Equivalents Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash $ 294,543 $ — $ — $ 294,543 $ 294,543 $ — $ — Level 2: Money market instruments 128,678 — — 128,678 128,678 — — Corporate debt securities 519,693 3,713 (67 ) 523,339 — 206,782 316,557 U.S. government agency securities 204,371 1,073 (97 ) 205,347 — 90,790 114,557 Foreign and other 549 142 (1 ) 690 — — 690 Subtotal 853,291 4,928 (165 ) 858,054 128,678 297,572 431,804 Total $ 1,147,834 $ 4,928 $ (165 ) $ 1,152,596 $ 423,220 $ 297,572 $ 431,804 As of December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Aggregate Fair Value Cash and Cash Equivalents Short-term Marketable Securities (1) Long-term Marketable Securities (2) Level 1: Cash $ 228,809 $ — $ — $ 228,809 $ 228,809 $ — $ — Level 2: Money market instruments 205,736 — — 205,736 205,736 — — Corporate debt securities 564,852 214 (2,288 ) 562,778 2,000 376,545 184,233 Commercial paper 77,702 — — 77,702 21,964 55,738 — U.S. government agency securities 240,436 144 (697 ) 239,883 31,474 156,967 51,442 Foreign and other 5,126 139 (1 ) 5,264 3,999 1,076 189 Subtotal 1,093,852 497 (2,986 ) 1,091,363 265,173 590,326 235,864 Total $ 1,322,661 $ 497 $ (2,986 ) $ 1,320,172 $ 493,982 $ 590,326 $ 235,864 (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 and five years.

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	9 Months Ended
	Sep. 30, 2019
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 $ 642,677 $ 307,995 Indefinite-lived intangible assets — 326,359 Gross intangible assets: 642,677 634,354 Less: Accumulated amortization (179,828 ) (142,546 ) Net carrying value $ 462,849 $ 491,808

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	9 Months Ended
	Sep. 30, 2019
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 $ 709,990 $ 694,447 Manufacturing and laboratory equipment 365,348 345,947 Computer hardware and software 165,235 157,787 Leasehold improvements 52,379 41,188 Furniture and equipment 37,603 33,234 Land improvements 7,239 6,551 Land 83,094 77,993 Construction-in-progress 84,021 64,170 1,504,909 1,421,317 Accumulated depreciation (535,609 ) (472,635 ) Total property, plant and equipment, net $ 969,300 $ 948,682

SUPPLEMENTAL BALANCE SHEET IN_2

SUPPLEMENTAL BALANCE SHEET INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Inventory	Inventory consisted of the following: September 30, December 31, Raw materials $ 68,391 $ 74,616 Work-in-process 321,073 231,064 Finished goods 219,585 225,191 Total inventory $ 609,049 $ 530,871
Schedule of Accounts Payable and Accrued Liabilities	Accounts Payable and Accrued Liabilities consisted of the following: September 30, 2019 December 31, 2018 Accounts payable and accrued operating expenses $ 226,769 $ 207,620 Accrued compensation expense 132,049 149,937 Accrued rebates payable 55,957 43,116 Accrued royalties payable 27,881 19,977 Value added taxes payable 7,556 7,785 Forward foreign currency exchange contracts 8,731 4,178 Lease liability 10,225 — Other 14,577 4,677 Total accounts payable and accrued liabilities $ 483,745 $ 437,290

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	9 Months Ended
	Sep. 30, 2019
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, 2019 and December 31, 2018 . 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, 2019 . Fair Value Measurements at September 30, 2019 Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets: Other current assets: NQDC Plan assets $ 1,135 $ — $ 1,135 Other assets: NQDC Plan assets 15,039 — 15,039 Restricted investments (1) 3,157 — 3,157 Total other assets 18,196 — 18,196 Total assets $ 19,331 $ — $ 19,331 Liabilities: Current liabilities: NQDC Plan liability (2) $ 1,135 $ — $ 1,135 Contingent consideration — 10,000 10,000 Total current liabilities 1,135 10,000 11,135 Other long-term liabilities: NQDC Plan liability (2) 15,039 — 15,039 Contingent consideration — 48,930 48,930 Total other long-term liabilities 15,039 48,930 63,969 Total liabilities $ 16,174 $ 58,930 $ 75,104 Fair Value Measurements at December 31, 2018 Quoted Price in Active Markets For Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Assets: Other current assets: NQDC Plan assets $ — $ 370 $ — $ 370 Restricted investments (1) — 9,581 — 9,581 Total other current assets — 9,951 — 9,951 Other assets: NQDC Plan assets — 12,828 — 12,828 Restricted investments (1) — 2,450 — 2,450 Strategic investments (3) 942 — — 942 Total other assets 942 15,278 — 16,220 Total assets $ 942 $ 25,229 $ — $ 26,171 Liabilities: Current liabilities: NQDC Plan liability $ 55 $ 370 $ — $ 425 Contingent consideration — — 85,951 85,951 Total current liabilities 55 370 85,951 86,376 Other long-term liabilities: NQDC Plan liability 17,598 12,828 — 30,426 Contingent consideration — — 46,883 46,883 Total other long-term liabilities 17,598 12,828 46,883 77,309 Total liabilities $ 17,653 $ 13,198 $ 132,834 $ 163,685 (1) The restricted investments at September 30, 2019 and December 31, 2018 secure the Company's irrevocable standby letters of credit obtained in connection with certain commercial agreements. (2) The Company’s NQDC Plan was amended during the second quarter of 2019, which resulted in a change to the classification of the obligation associated with the Company's common stock held in the NQDC Plan. The obligation was previously classified as a liability recorded at fair value and has been reclassified into equity and recorded at the shares' respective grant date fair values at June 30, 2019. The change to the NQDC Plan related to the prohibition of participants to diversify investments for deferrals of Company stock contributed into other types of investments. The NQDC Plan liabilities classified as Level 2 represent investments held in plan assets excluding shares of the Company's common stock. (3) The Company had investments in marketable equity securities measured using quoted prices in an active market that were considered strategic investments and were included in Other Assets on the Company's Condensed Consolidated Balance Sheets. During the second quarter of 2019, the Company realized an immaterial gain upon the sale of the shares.
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, 2018 $ 132,834 Changes in fair value of other contingent consideration 19,916 Milestone payments to Ares Trading S.A. (Merck Serono) (83,472 ) Milestone payments to former LEAD Therapeutics, Inc. shareholders (5,987 ) Realized gain on settlement of contingent consideration (1,928 ) Foreign exchange remeasurement of Euro denominated contingent consideration (2,433 ) Contingent consideration at September 30, 2019 $ 58,930

DERIVATIVE INSTRUMENTS AND HE_2

DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES (Tables)	9 Months Ended
	Sep. 30, 2019
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, 2019 December 31, 2018 Derivatives designated as hedging instruments: Asset Derivatives - Level 2 (1) Other current assets $ 29,900 $ 12,686 Other assets 22,892 10,324 Subtotal $ 52,792 $ 23,010 Liability Derivatives - Level 2 (1) Accounts payable and accrued liabilities $ 7,875 $ 4,036 Other long-term liabilities 7,641 3,653 Subtotal $ 15,516 $ 7,689 Derivatives not designated as hedging instruments: Asset Derivatives - Level 2 (1) Other current assets $ 71 $ 168 Other assets — — Subtotal $ 71 $ 168 Liability Derivatives - Level 2 (1) Accounts payable and accrued liabilities $ 858 $ 142 Other long-term liabilities — — Subtotal $ 858 $ 142 Total Derivatives Assets $ 52,863 $ 23,178 Total Derivatives Liabilities $ 16,374 $ 7,831 (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, 2018 .
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 Financial Statements for the period presented. Three Months Ended Nine Months Ended Derivatives Designated as Cash Flow Hedging Instruments September 30, 2019 September 30, 2019 Amount of Gain (Loss) Recognized in Other Comprehensive Income $ 23,973 $ 35,431 Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Derivatives Designated as Cash Flow Hedging Instruments Cash Flow Hedging Gains (Losses) Reclassified into Earnings Cash Flow Hedging Gains (Losses) Net product revenues as reported $ 450,900 $ 6,196 $ 1,224,458 $ 11,171 Operating expenses as reported $ 457,087 $ (1,388 ) $ 1,340,900 $ (1,885 ) Derivatives Not Designated as Hedging Instruments Gains (Losses) Recognized in Earnings Gains (Losses) Recognized in Earnings Operating Expenses $ (1,286 ) $ (5,182 )
Derivatives Designated As Hedging Instruments
Derivative [Line Items]
Summary of Derivatives Designated as Hedging Instruments Outstanding	The following table summarizes the Company’s derivatives designated as hedging instruments outstanding as of September 30, 2019 (notional amounts in millions): Foreign Exchange Contracts Number of Contracts Aggregate Notional Amount in Foreign Currency Maturity Australian Dollars – Sell 6 2.8 Oct 2019 - Dec 2019 Canadian Dollars – Sell 24 28.1 Oct 2019 - Sept 2020 Colombian Pesos – Sell 12 89,400.0 Oct 2019 - Sept 2020 Euros – Purchase 150 189.4 Oct 2019 - Sept 2022 Euros – Sell 453 624.2 Oct 2019 - Sept 2022 Norwegian Krone – Sell 3 11.7 Oct 2019 - Dec 2019 Total 648
Not Designated as Hedging Instrument
Derivative [Line Items]
Summary of Derivatives Designated as Hedging Instruments Outstanding	The following table summarizes the Company’s derivatives not designated as hedging instruments outstanding as of September 30, 2019 (notional amounts in millions): Foreign Exchange Contracts Number of Contracts Aggregate Notional Amount in Foreign Currency Maturity Colombian Pesos – Sell 2 96,000.0 Oct 2019 - Nov 2019 Euros – Purchase 2 44.1 Oct 2019 - Nov 2019 Great British Pounds - Purchase 1 4.9 Oct 2019 Great British Pounds - Sell 1 2.0 Oct 2019 Rubles – Sell 2 1,420.0 Oct 2019 - Nov 2019 Total 8

LEASES (Tables)

LEASES (Tables)	9 Months Ended
	Sep. 30, 2019
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, 2019 : Lease Classification Classification September 30, Assets: Operating Other Assets $ 51,284 Financing Other Assets 10,346 Total ROU assets $ 61,630 Liabilities: Current: Operating Accounts payable and accrued liabilities $ 7,273 Financing Accounts payable and accrued liabilities 2,952 Noncurrent: Operating Other long-term liabilities 45,499 Financing Other long-term liabilities 9,544 Total lease liabilities $ 65,268
Schedule of Maturities of Operating Lease Liabilities	Maturities of lease liabilities as of September 30, 2019 by fiscal year were as follows: Maturity of Lease Liabilities Operating Financing Total Remainder of 2019 $ 3,115 $ 3,204 $ 6,319 2020 9,925 3,464 13,389 2021 8,721 2,865 11,586 2022 8,406 2,258 10,664 2023 7,504 1,748 9,252 Thereafter 27,464 — 27,464 Total lease payments 65,135 13,539 78,674 Less: Interest (12,363 ) (1,043 ) (13,406 ) Present value of lease liabilities $ 52,772 $ 12,496 $ 65,268
Schedule of Maturities of Finance Lease Liabilities	Maturities of lease liabilities as of September 30, 2019 by fiscal year were as follows: Maturity of Lease Liabilities Operating Financing Total Remainder of 2019 $ 3,115 $ 3,204 $ 6,319 2020 9,925 3,464 13,389 2021 8,721 2,865 11,586 2022 8,406 2,258 10,664 2023 7,504 1,748 9,252 Thereafter 27,464 — 27,464 Total lease payments 65,135 13,539 78,674 Less: Interest (12,363 ) (1,043 ) (13,406 ) Present value of lease liabilities $ 52,772 $ 12,496 $ 65,268
Schedule of Lease Cost	Supplemental Cash Flow Information Nine Months Ended Cash paid for amounts included in the measurement of lease liabilities: Cash used in operating activities: Operating leases $ 5,918 Financing leases $ 454 Cash used in financing activities: Financing leases $ 2,027 ROU assets obtained in exchange for lease obligations: Operating leases $ 9,268 Financing leases $ 72 Lease Cost Classification Three Months Ended Nine Months Ended Operating (1) Operating Expenses $ 3,535 $ 9,946 Financing: Amortization Operating Expenses 600 1,811 Interest expense Operating Expenses 142 455 Total lease costs $ 4,277 $ 12,212 (1) Includes short-term leases and variable lease costs, both of which were not material.
Schedule of Other Information	Other Information September 30, Weighted average remaining lease term (in years): Operating leases 8.0 Financing leases 4.2 Weighted average discount rate: Operating leases 5.2 % Financing leases 5.4 %
Schedule of Minimum Lease Payments for Future Years	Minimum lease payments for future years as of December 31, 2018 were as follows: 2019 $ 12,976 2020 12,549 2021 11,198 2022 10,574 2023 9,993 Thereafter 27,701 Total $ 84,991

DEBT (Tables)

DEBT (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Summary of Convertible Debt	The following table summarizes information regarding the Company’s convertible debt: September 30, December 31, 1.50% senior subordinated convertible notes due in October 2020 (the 2020 Notes) 374,993 374,993 Unamortized discount (15,780 ) (26,581 ) Unamortized deferred offering costs (1,359 ) (2,334 ) Convertible Notes due in 2020, net 357,854 346,078 0.599% senior subordinated convertible notes due in August 2024 (the 2024 Notes) 495,000 495,000 Unamortized discount (6,887 ) (7,946 ) Unamortized deferred offering costs (2,351 ) (2,715 ) Convertible Notes due in 2024, net 485,762 484,339 Total convertible debt, net $ 843,616 $ 830,417 Fair value of fixed rate convertible debt Convertible Notes due in October 2020 (1) 384,713 419,722 Convertible Notes due in August 2024 (1) 490,297 491,626 Total fair value of fixed rate convertible debt $ 875,010 $ 911,348 (1) 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, 2018 .
Summary of Interest Expense on Debt	Interest expense on the Company’s convertible debt consisted of the following: Three Months Ended September 30, Nine Months Ended 2019 2018 2019 2018 Coupon interest expense $ 2,271 $ 3,331 $ 6,681 $ 9,819 Amortization of debt issuance costs 508 1,008 1,522 3,018 Accretion of discount on convertible notes 4,005 7,792 11,860 23,081 Total interest expense on convertible debt $ 6,784 $ 12,131 $ 20,063 $ 35,918

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (Tables)	9 Months Ended
	Sep. 30, 2019
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, 2019 and 2018 . Three Months Ended Nine Months Ended Condensed Consolidated Statement of Comprehensive Income (Loss) Classification 2019 2018 2019 2018 Gains (losses) on cash flow hedges: Forward contracts $ 6,196 $ 5,025 $ 11,171 $ (6,683 ) Net product revenues Forward contracts (1,388 ) 498 (1,885 ) 3,762 Operating expenses Total gain (loss) on cash flow hedges $ 4,808 $ 5,523 $ 9,286 $ (2,921 )
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, 2019 and 2018 . Three Months Ended September 30, 2019 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Available for-Sale Debt Securities Other Total AOCI balance at June 30, 2019 $ 14,181 $ 3,271 $ (13 ) $ 17,439 Other comprehensive income (loss) before reclassifications 23,973 522 (3 ) 24,492 Less: net 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, 2019 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Available for-Sale Debt Securities Other Total AOCI balance at December 31, 2018 $ 7,201 $ (1,917 ) $ (13 ) $ 5,271 Other comprehensive income (loss) before reclassifications 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 Three Months Ended September 30, 2018 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Available for-Sale Debt Securities Other Total AOCI balance at June 30, 2018 $ 2,568 $ (3,686 ) $ (11 ) $ (1,129 ) Other comprehensive income (loss) before 3,355 1,475 — 4,830 Less: gain (loss) reclassified from AOCI 5,523 — — 5,523 Tax effect — (338 ) — (338 ) Net current-period other comprehensive income (loss) (2,168 ) 1,137 — (1,031 ) AOCI balance at September 30, 2018 $ 400 $ (2,549 ) $ (11 ) $ (2,160 ) Nine Months Ended September 30, 2018 Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Available for-Sale Debt Securities Other Total AOCI balance at December 31, 2017 $ (20,232 ) $ (2,722 ) $ (7 ) $ (22,961 ) Impact of change in accounting principle — (586 ) — (586 ) AOCI balance at January 1, 2018 $ (20,232 ) $ (3,308 ) $ (7 ) $ (23,547 ) Other comprehensive income (loss) before 17,711 985 (4 ) 18,692 Less: gain (loss) reclassified from AOCI (2,921 ) — — (2,921 ) Tax effect — (226 ) — (226 ) Net current-period other comprehensive income (loss) 20,632 759 (4 ) 21,387 AOCI balance at September 30, 2018 $ 400 $ (2,549 ) $ (11 ) $ (2,160 )

REVENUE, CREDIT CONCENTRATION_2

REVENUE, CREDIT CONCENTRATIONS AND GEOGRAPHIC INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2019
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. Although Sanofi Genzyme (Genzyme) sells Aldurazyme worldwide, the 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. Genzyme is the Company’s sole customer for Aldurazyme and is responsible for marketing and selling Aldurazyme to third parties. Three Months Ended Nine Months Ended 2019 2018 2019 2018 Total revenues by geographic region: United States $ 201,874 $ 174,722 $ 562,217 $ 528,082 Europe 125,485 111,069 369,585 323,940 Latin America 83,799 75,400 164,132 151,955 Rest of world 49,939 30,515 153,671 134,021 Total revenues $ 461,097 $ 391,706 $ 1,249,605 $ 1,137,998
Schedule of Net Product Revenues by Product	The following table disaggregates Net Product Revenues by product. Three Months Ended Nine Months Ended 2019 2018 2019 2018 Net product revenues by product: Aldurazyme $ 22,852 $ 27,593 $ 73,945 $ 117,652 Brineura 19,840 9,936 46,815 27,743 Firdapse 5,668 4,977 16,262 15,080 Kuvan 120,524 113,254 340,771 321,414 Naglazyme 94,408 103,089 279,462 269,171 Palynziq 24,142 4,129 55,250 4,129 Vimizim 163,466 123,342 411,953 368,016 Total net product revenues $ 450,900 $ 386,320 $ 1,224,458 $ 1,123,205
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, the Company’s sole customer for Aldurazyme. Three Months Ended Nine Months Ended 2019 2018 2019 2018 United States $ 175,127 $ 146,742 $ 480,330 $ 409,294 Europe 121,363 107,851 358,041 315,270 Latin America 83,799 75,400 164,132 151,955 Rest of world 47,759 28,734 148,010 129,034 Total net product revenues marketed by the Company 428,048 358,727 1,150,513 1,005,553 Aldurazyme net product revenues marketed by Genzyme 22,852 27,593 73,945 117,652 Total net product revenues $ 450,900 $ 386,320 $ 1,224,458 $ 1,123,205
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 2019 2018 2019 2018 Customer A 16 % 16 % 17 % 17 % Customer B 13 % 12 % 12 % 12 % Customer C 10 % 10 % 11 % 10 % Customer D 5 % 7 % 6 % 11 % Customer E 12 % — % 6 % — % Customer F — % 13 % — % 6 % Total 56 % 58 % 52 % 56 %

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	9 Months Ended
	Sep. 30, 2019
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 September 30, Nine Months Ended 2019 2018 2019 2018 Cost of sales $ 4,093 $ 3,974 $ 12,629 $ 10,360 Research and development 14,261 14,257 43,037 43,099 Selling, general and administrative 20,819 18,815 66,097 58,802 Total stock-based compensation expense $ 39,173 $ 37,046 $ 121,763 $ 112,261
Schedule of Stock Option Valuation Assumptions	The assumptions used to estimate the per share fair value of stock options granted during the periods presented were as follows: Three Months Ended Nine Months Ended 2019 2018 2019 2018 Expected volatility N/A 36.8% 37.1 – 37.4% 36.8 – 38.4% Dividend yield N/A 0.0% 0.0% 0.0% Expected life (in years) N/A 5.7 4.6 – 5.8 4.6 – 5.7 Risk-free interest rate N/A 2.8% 2.2 – 3.0% 2.3 – 2.8%

NET LOSS PER COMMON SHARE (Tabl

NET LOSS PER COMMON SHARE (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per common share (in thousands of common shares): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Numerator: Net Income (Loss), basic $ 55,036 $ (12,620 ) $ (38,872 ) $ (73,561 ) Add: Interest on 2024 notes 937 — — — Net Income (Loss), diluted $ 55,973 $ (12,620 ) $ (38,872 ) $ (73,561 ) Denominator: Weighted-average common shares outstanding, basic 179,289 177,481 178,873 176,767 Effect of dilutive securities: Options to purchase common stock 1,560 — — — Common stock issuable under the 2024 notes 3,970 — — — Unvested RSUs 669 — — — Common stock potentially issuable for ESPP purchases 231 — — — Common shares held by the NQDC 205 — — — Weighted-average common shares outstanding, diluted 185,924 177,481 178,873 176,767 Net Income (Loss) per common share, basic 0.31 (0.07 ) (0.22 ) (0.42 ) Net Income (Loss) per common share, diluted 0.30 (0.07 ) (0.22 ) (0.42 )
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 using the if-converted or treasury stock method (in thousands of common shares): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Options to purchase common stock 5,829 7,517 7,388 7,517 Common stock issuable under the 2018 Notes — 3,983 — 3,983 Common stock issuable under the 2020 Notes 3,983 3,983 3,983 3,983 Common stock issuable under the 2024 Notes — 3,970 3,970 3,970 Unvested RSUs 3,360 3,411 4,029 3,411 Common stock potentially issuable for ESPP purchases 222 407 453 407 Common stock held by the NQDC — 208 205 208 Total number of potentially issuable shares 13,394 23,479 20,028 23,479

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019
Significant Accounting Policies [Line Items]
Lease ROU assets	$ 61,630
Lease liabilities	$ 65,268
ASC Topic 842
Significant Accounting Policies [Line Items]
Lease ROU assets		$ 55,900
Lease liabilities		$ 59,000

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, 2019	Dec. 31, 2018		Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,147,834	$ 1,322,661
Gross Unrealized Gains	4,928	497
Gross Unrealized Losses	(165)	(2,986)
Aggregate Fair Value	1,152,596	1,320,172
Cash and Cash Equivalents	423,220	493,982	[1]	$ 882,184	$ 598,028
Short-term Marketable Securities	297,572	590,326	[1]
Long-term Marketable Securities	431,804	235,864	[1]
Level 1: | Cash
Schedule of Available-for-sale Securities [Line Items]
Cash	294,543	228,809
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Aggregate Fair Value	294,543	228,809
Cash and Cash Equivalents	294,543	228,809
Short-term Marketable Securities	0	0
Long-term Marketable Securities	0	0
Level 2:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	853,291	1,093,852
Gross Unrealized Gains	4,928	497
Gross Unrealized Losses	(165)	(2,986)
Aggregate Fair Value	858,054	1,091,363
Cash and Cash Equivalents	128,678	265,173
Short-term Marketable Securities	297,572	590,326
Long-term Marketable Securities	431,804	235,864
Level 2: | Money market instruments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	128,678	205,736
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Aggregate Fair Value	128,678	205,736
Cash and Cash Equivalents	128,678	205,736
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	519,693	564,852
Gross Unrealized Gains	3,713	214
Gross Unrealized Losses	(67)	(2,288)
Aggregate Fair Value	523,339	562,778
Cash and Cash Equivalents	0	2,000
Short-term Marketable Securities	206,782	376,545
Long-term Marketable Securities	316,557	184,233
Level 2: | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		77,702
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Aggregate Fair Value		77,702
Cash and Cash Equivalents		21,964
Short-term Marketable Securities		55,738
Level 2: | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	204,371	240,436
Gross Unrealized Gains	1,073	144
Gross Unrealized Losses	(97)	(697)
Aggregate Fair Value	205,347	239,883
Cash and Cash Equivalents	0	31,474
Short-term Marketable Securities	90,790	156,967
Long-term Marketable Securities	114,557	51,442
Level 2: | Foreign and other
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	549	5,126
Gross Unrealized Gains	142	139
Gross Unrealized Losses	(1)	(1)
Aggregate Fair Value	690	5,264
Cash and Cash Equivalents	0	3,999
Short-term Marketable Securities	0	1,076
Long-term Marketable Securities	$ 690	$ 189
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]
Long term marketable securities maturity period	5 years	5 years
Short term marketable securities maturity period	1 year	1 year
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2019USD ($)
Investments, Debt and Equity Securities [Abstract]
Other- than- temporary impairment	$ 0

Intangible Assets (Detail)

Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gain on sale of intangible assets	$ 0	$ 15,000	$ 0	$ 15,000	$ 20,000
Intangible assets:
Finite-lived intangible assets	642,677			642,677		$ 307,995
Indefinite-lived intangible assets	0			0		326,359
Gross intangible assets:	642,677			642,677		634,354
Less: Accumulated amortization	(179,828)			(179,828)		(142,546)
Net carrying value	$ 462,849			$ 462,849		$ 491,808	[1]
Restatement Adjustment
Intangible assets:
Finite-lived intangible assets		326,400
Indefinite-lived intangible assets		$ (326,400)
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

Property Plant and Equipment -

Property Plant and Equipment - Schedule of Property Plant and Equipment Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,504,909	$ 1,421,317
Accumulated depreciation	(535,609)	(472,635)
Total property, plant and equipment, net	969,300	948,682	[1]
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	709,990	694,447
Manufacturing and laboratory equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	365,348	345,947
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	165,235	157,787
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	52,379	41,188
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	37,603	33,234
Land improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,239	6,551
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	83,094	77,993
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 84,021	$ 64,170
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

Property Plant and Equipment -

Property Plant and Equipment - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 24.2	$ 26.6	$ 67.2	$ 66.7
Depreciation capitalized into inventory	$ 9.8	$ 8.1	$ 24.9	$ 18.6

Supplemental Balance Sheet In_3

Supplemental Balance Sheet Information - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Inventory [Line Items]
Raw materials	$ 68,391	$ 74,616
Work-in-process	321,073	231,064
Finished goods	219,585	225,191
Total inventory	609,049	$ 530,871	[1]
Pre-Launch Valoctocogene Roxaparvovec
Inventory [Line Items]
Total inventory	$ 7,100
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

Supplemental Balance Sheet In_4

Supplemental Balance Sheet Information - Schedule of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts payable and accrued operating expenses	$ 226,769	$ 207,620
Accrued compensation expense	132,049	149,937
Accrued rebates payable	55,957	43,116
Accrued royalties payable	27,881	19,977
Value added taxes payable	7,556	7,785
Forward foreign currency exchange contracts	8,731	4,178
Lease liability	10,225	0
Other	14,577	4,677
Total accounts payable and accrued liabilities	$ 483,745	$ 437,290	[1]
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Financial Assets and Liabilities (Detail) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
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
Liabilities remeasured	0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		$ 9,951,000
Fair value of other non-current assets	18,196,000	16,220,000
Fair value of financial assets, Total	19,331,000	26,171,000
Fair value of other current liabilities	11,135,000	86,376,000
Fair value of other non-current liabilities	63,969,000	77,309,000
Fair value of financial liabilities, Total	75,104,000	163,685,000
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	1,135,000	425,000
Fair value of other non-current liabilities	15,039,000	30,426,000
Fair Value, Measurements, Recurring | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	10,000,000	85,951,000
Fair value of other non-current liabilities	48,930,000	46,883,000
Fair Value, Measurements, Recurring | Quoted Price in Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		0
Fair value of other non-current assets		942,000
Fair value of financial assets, Total		942,000
Fair value of other current liabilities		55,000
Fair value of other non-current liabilities		17,598,000
Fair value of financial liabilities, Total		17,653,000
Fair Value, Measurements, Recurring | Quoted Price in Active Markets For Identical Assets (Level 1) | NQDC Plan liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		55,000
Fair value of other non-current liabilities		17,598,000
Fair Value, Measurements, Recurring | Quoted Price in Active Markets For Identical Assets (Level 1) | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		0
Fair value of other non-current liabilities		0
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 current assets		9,951,000
Fair value of other non-current assets	18,196,000	15,278,000
Fair value of financial assets, Total	19,331,000	25,229,000
Fair value of other current liabilities	1,135,000	370,000
Fair value of other non-current liabilities	15,039,000	12,828,000
Fair value of financial liabilities, Total	16,174,000	13,198,000
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	1,135,000	370,000
Fair value of other non-current liabilities	15,039,000	12,828,000
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 current liabilities	0	0
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 current assets		0
Fair value of other non-current assets	0	0
Fair value of financial assets, Total	0	0
Fair value of other current liabilities	10,000,000	85,951,000
Fair value of other non-current liabilities	48,930,000	46,883,000
Fair value of financial liabilities, Total	58,930,000	132,834,000
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 current liabilities	10,000,000	85,951,000
Fair value of other non-current liabilities	48,930,000	46,883,000
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	1,135,000	370,000
Fair value of other non-current assets	15,039,000	12,828,000
Fair Value, Measurements, Recurring | NQDC Plan assets | Quoted Price in Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		0
Fair value of other non-current assets		0
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	1,135,000	370,000
Fair value of other non-current assets	15,039,000	12,828,000
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 current assets		9,581,000
Fair value of other non-current assets	3,157,000	2,450,000
Fair Value, Measurements, Recurring | Restricted Investments | Quoted Price in Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		0
Fair value of other non-current assets		0
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 current assets		9,581,000
Fair value of other non-current assets	3,157,000	2,450,000
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 current assets		0
Fair value of other non-current assets	$ 0	0
Fair Value, Measurements, Recurring | Strategic Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets		942,000
Fair Value, Measurements, Recurring | Strategic Investments | Quoted Price in Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets		942,000
Fair Value, Measurements, Recurring | Strategic 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		0
Fair Value, Measurements, Recurring | Strategic 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

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, 2019USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration at December 31, 2018	$ 132,834
Changes in fair value of other contingent consideration	19,916
Milestone payments to Ares Trading S.A. (Merck Serono)	(83,472)
Milestone payments to former LEAD Therapeutics, Inc. shareholders	(5,987)
Realized gain on settlement of contingent consideration	(1,928)
Foreign exchange remeasurement of Euro denominated contingent consideration	(2,433)
Contingent consideration at September 30, 2019	$ 58,930

Derivative Instruments and He_3

Derivative Instruments and Hedging Strategies - Summary of Derivatives Designated as Hedging Instruments Outstanding (Detail) - Derivatives Designated As Hedging Instruments - Foreign exchange contracts € in Millions, kr in Millions, $ in Millions, $ in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2019NOK (kr)Derivative	Sep. 30, 2019EUR (€)Derivative	Sep. 30, 2019COP ($)Derivative	Sep. 30, 2019AUD ($)Derivative	Sep. 30, 2019CAD ($)Derivative
Derivative [Line Items]
Number of Contracts	648	648	648	648	648
Australian Dollars | Sell
Derivative [Line Items]
Number of Contracts	6	6	6	6	6
Aggregate Notional Amount in Foreign Currency | $				$ 2.8
Australian Dollars | Minimum | Sell
Derivative [Line Items]
Maturity	Oct. 31, 2019
Australian Dollars | Maximum | Sell
Derivative [Line Items]
Maturity	Dec. 31, 2019
Canadian Dollars | Sell
Derivative [Line Items]
Number of Contracts	24	24	24	24	24
Aggregate Notional Amount in Foreign Currency | $					$ 28.1
Canadian Dollars | Minimum | Sell
Derivative [Line Items]
Maturity	Oct. 31, 2019
Canadian Dollars | Maximum | Sell
Derivative [Line Items]
Maturity	Sep. 30, 2020
Colombian Pesos | Sell
Derivative [Line Items]
Number of Contracts	12	12	12	12	12
Aggregate Notional Amount in Foreign Currency | $			$ 89,400
Colombian Pesos | Minimum | Sell
Derivative [Line Items]
Maturity	Oct. 31, 2019
Colombian Pesos | Maximum | Sell
Derivative [Line Items]
Maturity	Sep. 30, 2020
Euros | Sell
Derivative [Line Items]
Number of Contracts	453	453	453	453	453
Aggregate Notional Amount in Foreign Currency | €		€ 624.2
Euros | Purchase
Derivative [Line Items]
Number of Contracts	150	150	150	150	150
Aggregate Notional Amount in Foreign Currency | €		€ 189.4
Euros | Minimum | Sell
Derivative [Line Items]
Maturity	Oct. 31, 2019
Euros | Minimum | Purchase
Derivative [Line Items]
Maturity	Oct. 31, 2019
Euros | Maximum | Sell
Derivative [Line Items]
Maturity	Sep. 30, 2022
Euros | Maximum | Purchase
Derivative [Line Items]
Maturity	Sep. 30, 2022
Norwegian Krone | Sell
Derivative [Line Items]
Number of Contracts	3	3	3	3	3
Aggregate Notional Amount in Foreign Currency | kr	kr 11.7
Norwegian Krone | Minimum | Sell
Derivative [Line Items]
Maturity	Oct. 31, 2019
Norwegian Krone | Maximum | Sell
Derivative [Line Items]
Maturity	Dec. 31, 2019

Derivative Instruments and He_4

Derivative Instruments and Hedging Strategies - Summary of Derivatives Not Designated as Hedging Instruments Outstanding (Detail) - Not Designated as Hedging Instrument ₽ in Millions, € in Millions, £ in Millions, R$ in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2019RUB (₽)Derivative	Sep. 30, 2019EUR (€)Derivative	Sep. 30, 2019COP ($)Derivative	Sep. 30, 2019BRL (R$)Derivative	Sep. 30, 2019GBP (£)Derivative
Derivative [Line Items]
Number of Contracts	8	8	8	8	8
Colombian Pesos | Foreign exchange contracts | Sell
Derivative [Line Items]
Number of Contracts	2	2	2	2	2
Aggregate Notional Amount in Foreign Currency | R$				R$ 96000.0
Colombian Pesos | Minimum | Foreign exchange contracts | Sell
Derivative [Line Items]
Maturity	Oct. 31, 2019
Colombian Pesos | Maximum | Foreign exchange contracts | Sell
Derivative [Line Items]
Maturity	Nov. 30, 2019
Euros | Foreign exchange contracts | Purchase
Derivative [Line Items]
Number of Contracts	2	2	2	2	2
Aggregate Notional Amount in Foreign Currency | $			$ 44.1
Euros | Foreign exchange contracts | Sell
Derivative [Line Items]
Maturity	Jul. 31, 2019
Euros | Minimum | Foreign exchange contracts | Purchase
Derivative [Line Items]
Maturity	Oct. 31, 2019
Euros | Maximum | Foreign exchange contracts | Purchase
Derivative [Line Items]
Maturity	Nov. 30, 2019
Great British Pounds | Foreign exchange contracts | Purchase
Derivative [Line Items]
Number of Contracts	1	1	1	1	1
Aggregate Notional Amount in Foreign Currency | €		€ 4.9
Maturity	Oct. 31, 2019
Great British Pounds | Foreign exchange contracts | Sell
Derivative [Line Items]
Number of Contracts	1	1	1	1	1
Aggregate Notional Amount in Foreign Currency | £					£ 2
Maturity	Oct. 31, 2019
Rubles | Foreign exchange contracts | Sell
Derivative [Line Items]
Number of Contracts	2	2	2	2	2
Aggregate Notional Amount in Foreign Currency | ₽	₽ 1,420
Rubles | Minimum | Foreign exchange contracts | Sell
Derivative [Line Items]
Maturity	Oct. 31, 2019
Rubles | Maximum | Foreign exchange contracts | Sell
Derivative [Line Items]
Maturity	Nov. 30, 2019

Derivative Instruments and He_5

Derivative Instruments and Hedging Strategies - Fair Value Carrying Amount of Derivatives (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Asset, Fair Value	$ 52,863	$ 23,178
Derivative Liability, Fair Value	16,374	7,831
Level 2: | Derivatives Designated As Hedging Instruments
Derivative [Line Items]
Derivative Asset, Fair Value	52,792	23,010
Derivative Liability, Fair Value	15,516	7,689
Level 2: | Derivatives Designated As Hedging Instruments | Other current assets
Derivative [Line Items]
Derivative Asset, Fair Value	29,900	12,686
Level 2: | Derivatives Designated As Hedging Instruments | Other assets
Derivative [Line Items]
Derivative Asset, Fair Value	22,892	10,324
Level 2: | Derivatives Designated As Hedging Instruments | Accounts payable and accrued liabilities
Derivative [Line Items]
Derivative Liability, Fair Value	7,875	4,036
Level 2: | Derivatives Designated As Hedging Instruments | Other long-term liabilities
Derivative [Line Items]
Derivative Liability, Fair Value	7,641	3,653
Level 2: | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value	71	168
Derivative Liability, Fair Value	858	142
Level 2: | Not Designated as Hedging Instrument | Other current assets
Derivative [Line Items]
Derivative Asset, Fair Value	71	168
Level 2: | Not Designated as Hedging Instrument | Other assets
Derivative [Line Items]
Derivative Asset, Fair Value	0	0
Level 2: | Not Designated as Hedging Instrument | Accounts payable and accrued liabilities
Derivative [Line Items]
Derivative Liability, Fair Value	858	142
Level 2: | Not Designated as Hedging Instrument | Other long-term liabilities
Derivative [Line Items]
Derivative Liability, Fair Value	$ 0	$ 0

Derivative Instruments and He_6

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Net product revenues	$ 461,097	$ 391,706	$ 1,249,605	$ 1,137,998
Operating expenses as reported	457,087	407,447	1,340,900	1,223,374
Derivatives Designated As Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Other Comprehensive Income	23,973		35,431
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) Recognized in Earnings	(1,286)		(5,182)
Operating Expense | 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	(1,388)		(1,885)
Net product revenues
Derivative Instruments, Gain (Loss) [Line Items]
Net product revenues	450,900	$ 386,320	1,224,458	$ 1,123,205
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	$ 6,196		$ 11,171

Derivative Instruments and He_7

Derivative Instruments and Hedging Strategies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Amount reclassified from AOCI to earnings as related to forecasted revenue and operating expense transactions	$ 19.2

Leases - Schedule of ROU Assets

Leases - Schedule of ROU Assets and Lease Liabilities (Detail) $ in Thousands	Sep. 30, 2019USD ($)
Assets:
Operating	$ 51,284
Financing	10,346
Total ROU assets	61,630
Liabilities:
Operating, Current	7,273
Financing, Current	2,952
Operating, Noncurrent	45,499
Financing, Noncurrent	9,544
Total lease liabilities	$ 65,268

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Detail) $ in Thousands	Sep. 30, 2019USD ($)
Operating
Remainder of 2019	$ 3,115
2020	9,925
2021	8,721
2022	8,406
2023	7,504
Thereafter	27,464
Total lease payments	65,135
Less: Interest	(12,363)
Present value of lease liabilities	52,772
Financing
Remainder of 2019	3,204
2020	3,464
2021	2,865
2022	2,258
2023	1,748
Thereafter	0
Total lease payments	13,539
Less: Interest	(1,043)
Present value of lease liabilities	12,496
Total
Remainder of 2019	6,319
2020	13,389
2021	11,586
2022	10,664
2023	9,252
Thereafter	27,464
Total lease payments	78,674
Less: Interest	(13,406)
Present value of lease liabilities	$ 65,268

Leases - Schedule of Lease Cost

Leases - Schedule of Lease Cost (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lease Cost
Total lease costs	$ 4,277	$ 12,212
Operating Expenses
Lease Cost
Operating	3,535	9,946
Amortization	600	1,811
Interest expense	$ 142	$ 455

Leases - Schedule of Other Info

Leases - Schedule of Other Information (Detail)	Sep. 30, 2019USD ($)
Weighted average remaining lease term (in years):
Operating leases	8 years
Financing leases	4 years 2 months 12 days
Weighted average discount rate:
Operating leases	5.20%
Financing leases	5.40%
Additional leases not yet commenced (undiscounted):
Operating lease liability to commence in the remainder of 2019	$ 0

Leases - Schedule of Supplement

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

Leases - Schedule of Minimum Le

Leases - Schedule of Minimum Lease Payments for Future Years (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 12,976
2020	12,549
2021	11,198
2022	10,574
2023	9,993
Thereafter	27,701
Total	$ 84,991

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Leases [Abstract]
Rent expense	$ 12.2
Deferred rent accruals	2.1
Deferred rent accruals, current	$ 0.5

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	1 Months Ended	9 Months Ended
	Oct. 31, 2018	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Carrying value of equity component		$ 870,000,000
The 2018 Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 200,000,000
Maturity date of convertible debt	Oct. 19, 2021
To repay early, minimum required amount outstanding with certain other conditions have not been met	$ 100,000,000
Maturity date of credit facility, if certain other conditions have not been met	Aug. 1, 2020
Debt issuance costs	$ 1,000,000
Outstanding amount		$ 0	$ 0
The 2018 Credit Facility | LIBOR Rate
Debt Instrument [Line Items]
Interest rate on deemed loan description		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)
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%

Debt - Summary of Convertible D

Debt - Summary of Convertible Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Convertible Notes	$ 870,000
Convertible Notes, net of unamortized discount and deferred offering costs	843,616	$ 830,417	[1]
Total convertible debt, net	843,616	830,417
Total fair value of fixed rate convertible debt	$ 875,010	$ 911,348
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	(15,780)	(26,581)
Convertible debt, Unamortized deferred offering costs	(1,359)	(2,334)
Convertible Notes, net of unamortized discount and deferred offering costs	357,854	346,078
Total fair value of fixed rate convertible debt	$ 384,713	$ 419,722
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	(6,887)	(7,946)
Convertible debt, Unamortized deferred offering costs	(2,351)	(2,715)
Convertible Notes, net of unamortized discount and deferred offering costs	485,762	484,339
Total fair value of fixed rate convertible debt	$ 490,297	$ 491,626
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule Of Interest Expenses [Line Items]
Total interest expense on convertible debt	$ 2,937	$ 12,131	$ 16,530	$ 35,918
Convertible Senior Notes
Schedule Of Interest Expenses [Line Items]
Coupon interest expense	2,271	3,331	6,681	9,819
Amortization of debt issuance costs	508	1,008	1,522	3,018
Accretion of discount on convertible notes	4,005	7,792	11,860	23,081
Total interest expense on convertible debt	$ 6,784	$ 12,131	$ 20,063	$ 35,918

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net product revenues	$ 461,097	$ 391,706	$ 1,249,605	$ 1,137,998
Total gain (loss) on cash flow hedges	4,010	(15,741)	(91,295)	(85,376)
Net product revenues
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net product revenues	450,900	386,320	1,224,458	1,123,205
Amount Reclassified from AOCI Gain (Loss) | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total gain (loss) on cash flow hedges	4,808	5,523	9,286	(2,921)
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	(1,388)	498	(1,885)	3,762
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	$ 6,196	$ 5,025	$ 11,171	$ (6,683)

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, 2019	Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	[1]	$ 2,960,954	$ 2,885,104	$ 2,967,940	[2]	$ 2,808,663
Beginning Balance						(23,547)
Other comprehensive income (loss) before reclassifications		24,492	4,830	42,684		18,692
Less: gain (loss) reclassified from AOCI		4,808	5,523	9,286		(2,921)
Tax effect		(120)	(338)	(1,666)		(226)
Net current-period other comprehensive income (loss)		19,564	(1,031)	31,732		21,387
Ending Balance		3,074,405	2,914,945	3,074,405		2,914,945
ASU 2018-02
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Impact of change in accounting principle								$ (586)
Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		14,181	2,568	7,201		(20,232)
Beginning Balance						(20,232)
Other comprehensive income (loss) before reclassifications		23,973	3,355	35,431		17,711
Less: gain (loss) reclassified from AOCI		4,808	5,523	9,286		(2,921)
Tax effect		0	0	0		0
Net current-period other comprehensive income (loss)		19,165	(2,168)	26,145		20,632
Ending Balance		33,346	400	33,346		400
Unrealized Gains (Losses) on Cash Flow Hedges | ASU 2018-02
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Impact of change in accounting principle								0
Unrealized Gains (Losses) on Available for-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		3,271	(3,686)	(1,917)		(2,722)
Beginning Balance						(3,308)
Other comprehensive income (loss) before reclassifications		522	1,475	7,256		985
Less: gain (loss) reclassified from AOCI		0	0	0		0
Tax effect		(120)	(338)	(1,666)		(226)
Net current-period other comprehensive income (loss)		402	1,137	5,590		759
Ending Balance		3,673	(2,549)	3,673		(2,549)
Unrealized Gains (Losses) on Available for-Sale Debt Securities | ASU 2018-02
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Impact of change in accounting principle								(586)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		(13)	(11)	(13)		(7)
Beginning Balance						(7)
Other comprehensive income (loss) before reclassifications		(3)	0	(3)		(4)
Less: gain (loss) reclassified from AOCI		0	0	0		0
Tax effect		0	0	0		0
Net current-period other comprehensive income (loss)		(3)	0	(3)		(4)
Ending Balance		(16)	(11)	(16)		(11)
Other | ASU 2018-02
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Impact of change in accounting principle								$ 0
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	[1]	17,439	(1,129)	5,271		(22,961)
Impact of change in accounting principle							$ (586)
Ending Balance		$ 37,003	$ (2,160)	$ 37,003		$ (2,160)
[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 year ended December 31, 2018 , filed with the SEC on February 28, 2019.
[2]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

Revenue, Credit Concentration_3

Revenue, Credit Concentrations and Geographic Information - Additional Information (Detail) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)Segment	Dec. 31, 2018USD ($)
Concentration Risk And Geographic Information [Line Items]
Number of operating business segment | Segment	1
Accounts receivable, net	$ 402,970	$ 342,633	[1]
Customers
Concentration Risk And Geographic Information [Line Items]
Accounts receivable, net	$ 67,700	$ 73,900
Credit Concentration Risk | Accounts Receivable | Customer One
Concentration Risk And Geographic Information [Line Items]
Concentration risk, percentage	23.00%	30.00%
Credit Concentration Risk | Accounts Receivable | Customer Two
Concentration Risk And Geographic Information [Line Items]
Concentration risk, percentage	14.00%	16.00%
Credit Concentration Risk | Accounts Receivable | Customer Three
Concentration Risk And Geographic Information [Line Items]
Concentration risk, percentage	12.00%
[1]	December 31, 2018 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, 2018, filed with the SEC on February 28, 2019.

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue from External Customer [Line Items]
Total revenues	$ 461,097	$ 391,706	$ 1,249,605	$ 1,137,998
United States
Revenue from External Customer [Line Items]
Total revenues	201,874	174,722	562,217	528,082
Europe
Revenue from External Customer [Line Items]
Total revenues	125,485	111,069	369,585	323,940
Latin America
Revenue from External Customer [Line Items]
Total revenues	83,799	75,400	164,132	151,955
Rest of world
Revenue from External Customer [Line Items]
Total revenues	$ 49,939	$ 30,515	$ 153,671	$ 134,021

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue from External Customer [Line Items]
Net product revenues	$ 461,097	$ 391,706	$ 1,249,605	$ 1,137,998
Aldurazyme
Revenue from External Customer [Line Items]
Net product revenues	22,852	27,593	73,945	117,652
Brineura
Revenue from External Customer [Line Items]
Net product revenues	19,840	9,936	46,815	27,743
Firdapse
Revenue from External Customer [Line Items]
Net product revenues	5,668	4,977	16,262	15,080
Kuvan
Revenue from External Customer [Line Items]
Net product revenues	120,524	113,254	340,771	321,414
Naglazyme
Revenue from External Customer [Line Items]
Net product revenues	94,408	103,089	279,462	269,171
Palynziq
Revenue from External Customer [Line Items]
Net product revenues	24,142	4,129	55,250	4,129
Vimizim
Revenue from External Customer [Line Items]
Net product revenues	163,466	123,342	411,953	368,016
Total net product revenues
Revenue from External Customer [Line Items]
Net product revenues	$ 450,900	$ 386,320	$ 1,224,458	$ 1,123,205

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Net product revenues	$ 461,097	$ 391,706	$ 1,249,605	$ 1,137,998
United States
Disaggregation of Revenue [Line Items]
Net product revenues	201,874	174,722	562,217	528,082
Europe
Disaggregation of Revenue [Line Items]
Net product revenues	125,485	111,069	369,585	323,940
Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	83,799	75,400	164,132	151,955
Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	49,939	30,515	153,671	134,021
Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	22,852	27,593	73,945	117,652
Total net product revenues
Disaggregation of Revenue [Line Items]
Net product revenues	450,900	386,320	1,224,458	1,123,205
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim
Disaggregation of Revenue [Line Items]
Net product revenues	428,048	358,727	1,150,513	1,005,553
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | United States
Disaggregation of Revenue [Line Items]
Net product revenues	175,127	146,742	480,330	409,294
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Europe
Disaggregation of Revenue [Line Items]
Net product revenues	121,363	107,851	358,041	315,270
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	83,799	75,400	164,132	151,955
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	47,759	28,734	148,010	129,034
Marketed by Genzyme | Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	$ 22,852	$ 27,593	$ 73,945	$ 117,652

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Concentration Risk [Line Items]
Concentration risk, percentage	56.00%	58.00%	52.00%	56.00%
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	16.00%	16.00%	17.00%	17.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage	13.00%	12.00%	12.00%	12.00%
Customer C
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	10.00%	11.00%	10.00%
Customer D
Concentration Risk [Line Items]
Concentration risk, percentage	5.00%	7.00%	6.00%	11.00%
Customer E
Concentration Risk [Line Items]
Concentration risk, percentage	12.00%	0.00%	6.00%	0.00%
Customer F
Concentration Risk [Line Items]
Concentration risk, percentage	0.00%	13.00%	0.00%	6.00%

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 39,173	$ 37,046	$ 121,763	$ 112,261
Cost of sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4,093	3,974	12,629	10,360
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	14,261	14,257	43,037	43,099
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 20,819	$ 18,815	$ 66,097	$ 58,802

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
	Aug. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense capitalized to inventory				$ 5.1	$ 5.3	$ 13.2	$ 14.3
Shares issued under Employee Stock Purchase Plan (in shares)				0		107,473
Restricted Stock With Service Based Vesting Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, granted (in shares)						1,844,308
Weighted-average fair value per share granted (in dollars per share)						$ 91.23
Shares, granted (in shares)				0		610,250
Weighted-average fair value per RSU granted (in dollars per share)						$ 36.84
Two Thousand Twenty Two Base Restricted Stock Unit Awards With Performance Conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value per RSU granted (in dollars per share)	$ 81
Granted restricted stock units	44,260
March 2019 Base Restricted Stock Unit Awards with Performance Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value per RSU granted (in dollars per share)			$ 94.53
Granted restricted stock units			99,010
Award vesting service period		3 years
Percentage of annual threshold target			75.00%
Percentage of annual ceiling achievement			125.00%
March 2019 Base Restricted Stock Unit Awards with Performance Conditions | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of shares earned, performance metric			0.00%
March 2019 Base Restricted Stock Unit Awards with Performance Conditions | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of shares earned, performance metric			200.00%
March 2019 Base Restricted Stock Unit Awards with Market Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value per RSU granted (in dollars per share)			$ 143.92
Granted restricted stock units			99,010
Award vesting service period		3 years
Base percentage of annual target ceiling			100.00%
March 2019 Base 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%
March 2019 Base 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%

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Valuation Assumptions (Detail) - Options to purchase common stock	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	36.80%
Expected volatility, minimum		37.10%	36.80%
Expected volatility, maximum		37.40%	38.40%
Dividend yield	0.00%	0.00%	0.00%
Expected life (in years)	5 years 8 months 12 days
Risk-free interest rate	2.80%
Risk-free interest rate, minimum		2.20%	2.30%
Risk-free interest rate, maximum		3.00%	2.80%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)		4 years 7 months 6 days	4 years 7 months 6 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)		5 years 9 months 18 days	5 years 8 months 12 days

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Valuation allowance against a deferred tax asset					$ 29,600
Net tax expense (benefit)	$ (45,200)	$ (27,100)	$ (59,780)	$ (32,735)

NET LOSS PER COMMON SHARE Net L

NET LOSS PER COMMON SHARE Net 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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net Income (Loss), basic	$ 55,036	$ (12,620)	$ (38,872)	$ (73,561)
Net Income (Loss), diluted	$ 55,973	$ (12,620)	$ (38,872)	$ (73,561)
Denominator:
Weighted average number of shares outstanding, basic	179,289	177,481	178,873	176,767
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Weighted-average common shares outstanding, diluted	185,924	177,481	178,873	176,767
Net Income (Loss) per common share, basic (in dollars per share)	$ 0.31	$ (0.07)	$ (0.22)	$ (0.42)
Net Income (Loss) per common share, diluted (in dollars per share)	$ 0.30	$ (0.07)	$ (0.22)	$ (0.42)
Common stock issuable under the 2024 Notes
Numerator:
Add: Interest on 2024 notes	$ 937	$ 0	$ 0	$ 0
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	3,970	0	0	0
Options to purchase common stock
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	1,560	0	0	0
Unvested restricted stock units
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	669	0	0	0
Common stock potentially issuable for ESPP purchases
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	231	0	0	0
Common stock held by the NQDC
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Effect of dilutive securities	205	0	0	0

Net Loss Per Common Share - Sch

Net 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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	13,394	23,479	20,028	23,479
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	5,829	7,517	7,388	7,517
Common stock issuable under the 2018 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 2020 Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	3,983	3,983	3,983	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	3,970	3,970	3,970
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of potentially issuable shares (in shares)	3,360	3,411	4,029	3,411
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)	222	407	453	407
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	208	205	208

Net Loss Per Common Share - Add

Net Loss Per Common Share - Additional Information (Detail) - $ / shares	Sep. 30, 2019	Sep. 30, 2018
Convertible Notes due 2020
Earnings Per Share [Line Items]
Debt instrument, convertible, conversion price, per share (in dollars per share)	$ 94.15
Convertible Notes due 2018
Earnings Per Share [Line Items]
Debt instrument, interest rate, stated percentage, per annum		0.75%

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain development and regulatory activities and commercial sales and licensing milestones	$ 376.9
Contingent liabilities	69.1
Contingent liabilities short-term	20.2
Clinical and Post Marketing Services
Commitments And Contingencies [Line Items]
Purchase commitments and other minimum contractual obligations	131.6
Third Party
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain development and regulatory activities and commercial sales and licensing milestones	65.5
Completed Programs | Third Party
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain development and regulatory activities and commercial sales and licensing milestones	$ 239.7

Uncategorized Items - bmrn-30se

Label	Element	Value
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 20,634,000
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (2,727,000)