BioMarin Pharmaceutical (BMRN) 10-Q 5 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 24, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	BMRN
Entity Registrant Name	BIOMARIN PHARMACEUTICAL INC
Entity Central Index Key	1048477
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		160,336,762

CONDENSED_CONSOLIDATED_BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$900,570	$875,486	[1]
Short-term investments	108,119	69,706	[1]
Accounts receivable, net (allowance for doubtful accounts: $489 and $490, at March 31, 2015 and December 31, 2014, respectively)	175,738	144,472	[1]
Inventory	222,833	199,452	[1]
Current deferred tax assets	31,203	31,203	[1]
Other current assets	84,265	111,835	[1]
Total current assets	1,522,728	1,432,154	[1]
Noncurrent assets:
Investment in BioMarin/Genzyme LLC	890	1,039	[1]
Long-term investments	223,920	97,856	[1]
Property, plant and equipment, net	538,117	523,516	[1]
Intangible assets, net	926,896	156,578	[1]
Goodwill	202,392	54,258	[1]
Long-term deferred tax assets	163,411	159,771	[1]
Other assets	80,332	65,281	[1]
Total assets	3,658,686	2,490,453	[1]
Current liabilities:
Accounts payable and accrued liabilities	230,212	231,844	[1]
Short-term contingent acquisition consideration payable	75,294	3,895	[1]
Total current liabilities	305,506	235,739	[1]
Noncurrent liabilities:
Long-term convertible debt	655,491	657,976	[1]
Long-term contingent acquisition consideration payable	39,052	38,767	[1]
Long-term deferred tax liabilities	193,202
Other long-term liabilities	39,980	30,077	[1]
Total liabilities	1,233,231	962,559	[1]
Stockholders’ equity:
Common stock, $0.001 par value: 250,000,000 shares authorized at March 31, 2015 and December 31, 2014: 160,282,313 and 149,093,647 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	161	149	[1]
Additional paid-in capital	3,308,137	2,359,744	[1]
Company common stock held by Nonqualified Deferred Compensation Plan	-9,391	-9,695	[1]
Accumulated other comprehensive income	43,819	27,466	[1]
Accumulated deficit	-917,271	-849,770	[1]
Total stockholders’ equity	2,425,455	1,527,894	[1]
Total liabilities and stockholders’ equity	$3,658,686	$2,490,453	[1]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

CONDENSED_CONSOLIDATED_BALANCE1

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$489	$490	[1]
Common stock, par value	$0.00	$0.00	[1]
Common stock, shares authorized	250,000,000	250,000,000	[1]
Common stock, shares issued	160,282,313	149,093,647	[1]
Common stock, shares outstanding	160,282,313	149,093,647	[1]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

CONDENSED_CONSOLIDATED_STATEME

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
REVENUES:
Net product revenues	$201,312	$149,004
Collaborative agreement revenues	376	415
Royalty, license and other revenues	1,576	2,133
Total revenues	203,264	151,552
OPERATING EXPENSES:
Cost of sales	32,813	22,816
Research and development	142,074	86,166
Selling, general and administrative	92,806	60,069
Intangible asset amortization and contingent consideration	1,431	8,957
Total operating expenses	269,124	178,008
LOSS FROM OPERATIONS	-65,860	-26,456
Equity in the loss of BioMarin/Genzyme LLC	-150	-338
Interest income	683	1,123
Interest expense	-9,462	-9,106
Debt conversion expense	-163
Other income	249	153
LOSS BEFORE INCOME TAXES	-74,703	-34,624
Provision for (benefit from) income taxes	-7,202	3,491
NET LOSS	-67,501	-38,115
NET LOSS PER SHARE, BASIC	($0.43)	($0.26)
NET LOSS PER SHARE, DILUTED	($0.43)	($0.27)
Weighted average common shares outstanding, basic	157,612	143,983
Weighted average common shares outstanding, diluted	157,612	144,157
COMPREHENSIVE LOSS	($51,148)	($35,858)

CONDENSED_CONSOLIDATED_STATEME1

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	($67,501)		($38,115)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	14,397		12,004
Non-cash interest expense	7,000		6,698
Accretion of discount on investments	417		1,900
Stock-based compensation	23,714		17,267
Gain on termination of lease			-8,858
Equity in the loss of BioMarin/Genzyme LLC	150		338
Deferred income taxes	-7,800		-179
Excess tax benefit from stock option exercises	-527		-278
Unrealized foreign exchange gain on forward contracts	-5,686		1,323
Non-cash changes in the fair value of contingent acquisition consideration payable	282		8,151
Debt conversion expense	163
Other	-443
Changes in operating assets and liabilities:
Accounts receivable, net	-26,789		7,406
Inventory	-23,946		-13,870
Other current assets	-3,522		-927
Other assets	330		-920
Accounts payable and accrued liabilities	-57,236		-19,020
Other long-term liabilities	9,186		587
Net cash used in operating activities	-137,811		-26,493
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	-43,832		-23,607
Maturities and sales of investments	124,137		69,391
Purchase of available-for-sale investments	-288,431		-84,306
Purchase of promissory note	-3,326
Business acquisitions, net of cash acquired	-538,392
Other	-1,027
Net cash used in investing activities	-750,871		-38,522
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercises of stock options and Employee Stock Purchase Plan (the ESPP)	28,026		19,712
Taxes paid related to net share settlement of equity awards	-735		-473
Proceeds from public offering of common stock, net	888,257		117,464
Excess tax benefit from stock option exercises	527		278
Payments for debt conversion	-163
Other	-1,121		-17
Net cash provided by financing activities	914,791		136,964
Effect of exchange rate changes on cash	-1,025		-952
NET INCREASE IN CASH AND CASH EQUIVALENTS	25,084		70,997
Cash and cash equivalents:
Beginning of period	875,486	[1]	568,781
End of period	900,570		639,778
SUPPLEMENTAL CASH FLOW DISCLOSURES:
Cash paid for interest, net of interest capitalized into fixed assets	309		1
Cash paid for income taxes	1,358		381
Stock-based compensation capitalized into inventory	2,480		2,053
Depreciation capitalized into inventory	3,580		2,924
SUPPLEMENTAL CASH FLOW DISCLOSURES FROM INVESTING AND FINANCING ACTIVITIES:
Decrease in accounts payable and accrued liabilities related to fixed assets	-20,985		-9,171
Conversion of convertible debt	8,133
Deferred offering costs reclassified into additional paid-in-capital as a result of conversion of convertible debt	45
Release of escrow balance for purchase of San Rafael Corporate Center			$116,500
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

NATURE_OF_OPERATIONS_AND_BUSIN

NATURE OF OPERATIONS AND BUSINESS RISKS	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
NATURE OF OPERATIONS AND BUSINESS RISKS	(1) NATURE OF OPERATIONS AND BUSINESS RISKS
	BioMarin Pharmaceutical Inc. (the Company or BioMarin), a Delaware corporation, develops and commercializes innovative biopharmaceuticals for serious diseases and medical conditions. BioMarin 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 product portfolio is comprised of five approved products and multiple clinical and pre-clinical product candidates. The Company’s approved products are Vimizim (elosulfase alpha), Naglazyme (galsulfase), Kuvan (sapropterin dihydrochloride), Aldurazyme (laronidase) and Firdapse (amifampridine phosphate).
	Through March 31, 2015, the Company had accumulated losses of approximately $917.3 million. The Company expects to continue to finance future cash needs that exceed its operating activities primarily through its current cash, cash equivalents, short-term and long-term investments, and to the extent necessary, through proceeds from equity or debt financings, loans and 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.
	The Company is subject to a number of risks, including: the financial performance of Vimizim, Naglazyme, Kuvan, Aldurazyme and Firdapse; the potential need for additional financings; the Company’s ability to successfully commercialize its approved product candidates; the uncertainty of the Company’s research and development (R&D) efforts resulting in future successful commercial products; the Company’s ability to successfully obtain regulatory approval for new products; significant competition from larger organizations; reliance on the proprietary technology of others; dependence on key personnel; uncertain patent protection; dependence on corporate partners and collaborators; and possible restrictions on reimbursement from governmental agencies and healthcare organizations, as well as other changes in the health care industry.

BASIS_OF_PRESENTATION

BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
BASIS OF PRESENTATION	(2) BASIS OF PRESENTATION
	The accompanying Condensed Consolidated Financial Statements have been prepared pursuant to 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. generally accepted accounting principles (U.S. GAAP) for complete financial statements. 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, 2014 included in the Company’s Annual Report on Form 10-K.
	The accompanying Condensed Consolidated Financial Statements have been prepared in accordance with U.S. GAAP, which requires management to make estimates and assumptions that affect amounts reported in the Condensed Consolidated Financial Statements and accompanying disclosures. Although these estimates are based on management’s best knowledge of current events and actions that the Company may undertake in the future, actual results may be different from those estimates. The Condensed Consolidated Financial Statements reflect all adjustments of a normal, recurring nature that are, in the opinion of management, necessary for a fair presentation of results for these interim periods. The results of operations for the three months ended March 31, 2015 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2015.
	The Company has evaluated events and transactions subsequent to the balance sheet date. Based on this evaluation, the Company is not aware of any events or transactions that occurred subsequent to the balance sheet date but prior to filing this Quarterly Report on Form 10-Q that would require recognition or disclosure in the Condensed Consolidated Financial Statements.

SIGNIFICANT_ACCOUNTING_POLICIE

SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
SIGNIFICANT ACCOUNTING POLICIES	(3) SIGNIFICANT ACCOUNTING POLICIES
	There have been no material changes to the Company’s significant accounting policies during the three months ended March 31, 2015, as compared to the significant accounting policies disclosed in Note 3 of the Consolidated Financial Statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.
	Reclassifications
	Certain items in the Company’s prior year Condensed Consolidated Financial Statements have been reclassified to conform to the current presentation.

RECENT_ACCOUNTING_PRONOUNCEMEN

RECENT ACCOUNTING PRONOUNCEMENTS	3 Months Ended
	Mar. 31, 2015
Accounting Changes And Error Corrections [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	(4) RECENT ACCOUNTING PRONOUNCEMENTS
	There have been no new accounting pronouncements or changes to accounting pronouncements during the three months ended March 31, 2015, 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, 2014, that are of significance or potential significance to the Company.

ACQUISITIONS

ACQUISITIONS	3 Months Ended
	Mar. 31, 2015
Business Combinations [Abstract]
ACQUISITIONS	(5) ACQUISITIONS
	Prosensa Holding N.V.
	On January 29 2015, the Company completed the acquisition of Prosensa Holding N.V. (Prosensa), a public limited liability company organized under the laws of the Netherlands, for a total purchase price of $751.5 million. In connection with the acquisition of Prosensa, the Company recognized transaction costs of $9.7 million, of which $2.7 million and $7.0 million, respectively, was recognized in the year ended December 31, 2014 and the three months ended March 31, 2015.
	Prosensa was an innovative biotechnology company engaged in the discovery and development of ribonucleic acid (RNA)-modulating therapeutics for the treatment of genetic disorders. Prosensa’s primary focus was on rare neuromuscular and neurodegenerative disorders with a large unmet medical need, including subsets of patients with Duchenne muscular dystrophy (DMD), myotonic dystrophy and Huntington’s disease. Prosensa’s clinical portfolio of RNA-based product candidates was focused on the treatment of DMD. Each of Prosensa’s DMD compounds has been granted orphan drug status in the United States (the U.S.) and the European Union (the EU). Prosensa’s lead product, drisapersen, is currently under a rolling review as part of a rolling new drug application (NDA) with the Food and Drug Administration (the FDA). On April 27, 2015, the Company announced the completion of the rolling submission of the NDA to the FDA. The Company expects to file a marketing authorization application (MAA) for drisapersen with the European Medicines Agency (the EMA) in the summer of 2015.
	In connection with its acquisition of Prosensa, the Company made cash payments totaling $680.1 million which were comprised of $620.7 million for approximately 96.8% of Prosensa’s ordinary shares (the Prosensa Shares), $38.6 million for the options that vested pursuant to the Company’s tender offer for the Prosensa Shares and $20.8 million to the remaining Prosensa shareholders that did not tender their shares under the tender offer. Additionally, for each Prosensa Share, the Company issued one non-transferable contingent value right (the CVR), which represents the contractual right to receive a cash payment of up to $4.14 per Prosensa Share, or approximately $160.0 million (undiscounted), upon the achievement of certain product approval milestones. The fair value of the CVRs and acquired in-process research and development (IPR&D) on the acquisition date was $71.4 million and $772.8 million, respectively. The acquisition date fair value of the CVRs and IPR&D was estimated by applying a probability-based income approach utilizing an appropriate discount rate. Key assumptions include a discount rate and various probability factors. See Note 15 to these Condensed Consolidated Financial Statements for additional discussion regarding fair value measurements of the CVRs which is included in contingent acquisition consideration payable.
	The following table presents the allocation of the purchase consideration for the Prosensa acquisition, including the CVRs, based on fair value.
	Cash and cash equivalents	$	141,669
	Trade accounts receivable		3,086
	Other current assets		1,537
	Property, plant and equipment		2,683
	Intangible assets		497
	Other assets		104
	Acquired IPR&D		772,808
	Total identifiable assets acquired		922,384
	Accounts payable and accrued expenses		(68,799	)
	Debt assumed		(57,053	)
	Deferred tax liability		(193,202	)
	Total liabilities assumed		(319,054	)
	Net identifiable assets acquired		603,330
	Goodwill		148,134
	Net assets acquired	$	751,464
	A substantial portion of the assets acquired consisted of IPR&D related to Prosensa’s product candidates drisapersen and exons PRO 044 and PRO 045, which are considered to be indefinite-lived assets until completion or abandonment of the associated research and development (R&D) efforts. The Company determined that the estimated acquisition-date fair value of the intangible assets related to drisapersen and Prosensa’s other primary product candidates, PRO 044 and PRO-045 was $731.8 million, $16.9 million and $24.1 million, respectively.
	The deferred tax liability relates to the tax impact of future amortization or possible impairments associated with the identified intangible assets acquired, which are not deductible for tax purposes.
	Prosensa’s results of operations prior to and since the acquisition date are insignificant to the Company’s Condensed Consolidated Financial Statements.
	See Note 10 to these Condensed Consolidated Financial Statements for further discussion of the indefinite-lived intangible assets.
	San Rafael Corporate Center
	In March 2014, the Company completed the acquisition of the real estate commonly known as the San Rafael Corporate Center (SRCC), located in San Rafael, California. SRCC is a multi-building, commercial property where, prior to the acquisition, the Company was leasing a certain portion of the space for its headquarters and related operating activities. The purpose of this acquisition is to allow for future expansion of the Company’s corporate headquarters to accommodate anticipated headcount growth. The acquisition of SRCC has been accounted for as a business combination because the building and the in-place leases met the definition of a business in Accounting Standards Codification 805 (ASC 805), Business Combinations. The fair value of the consideration paid for SRCC was $116.5 million, all of which was paid in cash, which was held in escrow as of December 31, 2013.
	The following table summarizes the estimated fair values of assets acquired as of the date of acquisition:
		Estimated			Estimated
		Fair Value			Useful Lives
	Building and improvements	$	94,414		50 years
	Land		14,565
	Land improvements		3,616		10 years
	Intangible assets		3,905		Remaining
					lease terms
	Total identifiable net assets	$	116,500
	The fair values assigned to tangible and identifiable intangible assets acquired are based on management’s estimates and assumptions using the information that was available as of the date of the acquisition. The Company believes that the information provides a reasonable basis for estimating the fair values of assets acquired.
	The following table sets forth the fair value of the components of the identifiable intangible assets acquired by asset class as of the date of acquisition:
	Above market leases	$	351
	In-place leases		3,554
	Total intangible assets subject to amortization	$	3,905
	The value of any in-place leases is estimated to be equal to the property owners’ avoidance of costs necessary to release the property for a lease term equal to the remaining primary in-place lease term and the value of investment-grade tenancy, which is derived by estimating, based on a review of the market, the cost to be borne by a property owner to replicate a market lease for the remaining in-place term. These costs consist of: (i) rent lost during downtime (e.g., assumed periods of vacancy), (ii) estimated expenses that would be incurred by the property owner during periods of vacancy, (iii) rent concessions (e.g., free rent), (iv) leasing commissions and (v) tenant improvement allowances. The Company determined these values using management’s estimates along with third-party appraisals. The Company will amortize the capitalized value of in-place lease intangible assets to expense over the remaining initial term of each lease. The Company will amortize the capitalized value of above market leases to expense over the remaining lives of the underlying leases.
	The amount of third-party tenant revenue (included in the line item Royalty, License and Other Revenues) included in the Company’s Consolidated Statements of Comprehensive Loss for the three months ended March 31, 2015, was $1.0 million, compared to $0.4 million for the three months ended March 31, 2014. The amount of net income/loss from third-party tenants for the three months ended March 31, 2015 and 2014, was insignificant to the Company’s Consolidated Statement of Comprehensive Loss.
	SRCC’s results of operations prior to the acquisition were insignificant to the Company’s Condensed Consolidated Financial Statements.
	Included in Selling, General and Administrative (SG&A) expenses during the three months ended March 31, 2014 are transaction costs incurred in connection with the acquisition of SRCC of $0.2 million. The Company recognized a gain of $8.8 million in the three months ended March 31, 2014, due to the early termination of the Company’s pre-existing lease and the realization of the remaining balance in deferred rent and the reversal of the related asset retirement obligation upon acquisition of the SRCC. $2.7 million and $6.1 million of the gain were included in SG&A and R&D expenses, respectively, which is consistent with the Company’s allocation practices for facility costs for this previously leased space.

STOCKHOLDERS_EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
STOCKHOLDERS' EQUITY	(6) STOCKHOLDERS’ EQUITY
	In January 2015, the Company sold 9,775,000 shares of its common stock at a price of $93.25 per share in an underwritten public offering pursuant to an effective registration statement previously filed with the SEC. The Company received net proceeds of approximately $888.3 million from this public offering after underwriter’s discount and offering costs.

NET_LOSS_PER_COMMON_SHARE

NET LOSS PER COMMON SHARE	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
NET LOSS PER COMMON SHARE	(7) NET 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 Amended and Restated 2006 ESPP, unvested restricted stock, common stock held by the Company’s Nonqualified Deferred Compensation Plan (the NQDC) 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 March 31,
		2015			2014
	Numerator:
	Net loss, basic	$	(67,501	)	$	(38,115	)
	Gain on Company common stock issued to the NQDC		—			(374	)
	Net loss, diluted	$	(67,501	)	$	(38,489	)
	Denominator:
	Weighted-average common shares outstanding, basic		157,612			143,983
	Effect of dilutive securities:
	Common stock issued to the NQDC		—			174
	Weighted-average common shares outstanding, diluted		157,612			144,157
	Net loss per common share, basic	$	(0.43	)	$	(0.26	)
	Net loss per common share, diluted	$	(0.43	)	$	(0.27	)
	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 as they were anti-dilutive using the treasury stock method (in thousands of common shares):
		Three Months Ended March 31,
		2015			2014
	Options to purchase common stock		11,109			12,444
	Common stock issuable under the 2017 Notes		1,567			3,047
	Common stock issuable under the 2018 and 2020 Notes		7,966			7,966
	Unvested restricted stock units		1,557			1,326
	Potentially issuable common stock for ESPP purchases		223			209
	Common stock held by the NQDC		213			—
	Total number of potentially issuable shares		22,635			24,992
	The effect of the Company’s 0.75% senior subordinated convertible notes due in 2018 (the 2018 Notes) and the Company’s 1.50% senior subordinated convertible notes due in 2020 (the 2020 Notes and together with the 2018 Notes, the Notes) was excluded from the diluted net loss per common share since they may be settled in cash or shares at the Company’s option and the Company’s current intention is to settle up to the principal amount of the converted notes in cash and any excess conversion value (conversion spread) in shares of the Company’s common stock. As a result, during the three months ended March 31, 2014 the 2018 Notes and the 2020 Notes had no effect on diluted net loss per share until the Company’s stock price exceeded the conversion price of $94.15 per share for the Notes. Although the Company’s stock price exceeded the conversion price at March 31, 2105, the potential shares issuable under the Notes were excluded from the calculation of diluted loss per share as they were anti-dilutive using the if-converted method.

INVESTMENTS

INVESTMENTS	3 Months Ended
	Mar. 31, 2015
Investments Schedule [Abstract]
INVESTMENTS	(8) INVESTMENTS
	All investments were classified as available-for-sale at March 31, 2015 and December 31, 2014. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale securities by major security type at March 31, 2015 and December 31, 2014 are summarized in the tables below:
		Amortized Cost		Gross		Gross			Aggregate Fair
				Unrealized		Unrealized			Value at March 31, 2015
				Holding Gains		Holding Losses
	Certificates of deposit	$	69,871	$	1	$	—		$	69,872
	Corporate debt securities		147,537		129		—			147,666
	Commercial paper		21,354		—		—			21,354
	U.S. government agency securities		93,012		31		—			93,043
	Greek government-issued bonds		50		54		—			104
	Total	$	331,824	$	215	$	—		$	332,039
		Amortized Cost		Gross		Gross			Aggregate Fair
				Unrealized		Unrealized			Value at
				Holding Gains		Holding Losses			31-Dec-14
	Certificates of deposit	$	72,302	$	1	$	—		$	72,303
	Corporate debt securities		95,478		—		(342	)		95,136
	Greek government-issued bonds		50		73		—			123
	Total	$	167,830	$	74	$	(342	)	$	167,562
	The Company has two investments in marketable equity securities measured using quoted prices in their respective active markets and certain interest in non-marketable equity securities that are collectively considered strategic investments. As of March 31, 2015, the fair value of the Company’s marketable equity securities was $41.8 million, which included an unrealized gain of $29.3 million. The carrying cost of the non-marketable securities was $3.1 million at March 31, 2015. As of December 31, 2014, the fair value of the Company’s marketable equity securities was $30.8 million, which included an unrealized gain of $18.3 million. These investments are recorded in Other Assets in the Company’s Condensed Consolidated Balance Sheets.
	The fair values of available-for-sale securities by contractual maturity were as follows:
		March 31,		December 31,
		2015		2014
	Maturing in one year or less	$	108,119	$	69,706
	Maturing after one year through five years		223,920		97,856
	Total	$	332,039	$	167,562
	Impairment assessments are made at the individual security level each reporting period. When the fair value of an investment is less than its cost at the balance sheet date, a determination is made as to whether the impairment is other-than-temporary and, if it is other-than-temporary, an impairment loss is recognized in earnings equal to the difference between the investment’s amortized cost and fair value at such date. As of March 31, 2015, some of the Company’s investments were in an unrealized loss position. However, the Company has the ability and intent to hold all investments that have been in a continuous loss position until maturity or recovery, thus no other-than-temporary impairment is deemed to have occurred.
	See Note 15 to these Condensed Consolidated Financial Statements for additional discussion regarding the fair value of the Company’s available-for-sale securities.

GOODWILL

GOODWILL	3 Months Ended
	Mar. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
GOODWILL	(9) GOODWILL
	Goodwill is tested for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in the circumstances that would indicate a reduction in the fair value of the goodwill below its carrying amount.
	The following table represents the changes in goodwill for the three months ended March 31, 2015:
	Balance at December 31, 2014	$	54,258
	Addition of goodwill related to the acquisition of Prosensa		148,134
	Balance at March 31, 2015	$	202,392

INTANGIBLE_ASSETS

INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	(10) INTANGIBLE ASSETS
	Intangible assets consisted of the following:
		March 31,			December 31,
		2015			2014
	Intangible assets:
	Finite-lived intangible assets	$	123,836		$	123,365
	Indefinite-lived intangible assets		847,238			74,430
	Gross intangible assets:		971,074			197,795
	Less: Accumulated amortization		(44,178	)		(41,217	)
	Net carrying value	$	926,896		$	156,578
	Indefinite-Lived Intangible Assets
	IPR&D assets are considered to be indefinite-lived until the completion or abandonment of the associated R&D efforts. During the period the assets are considered indefinite-lived, they will not be amortized but will be tested for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in circumstances that would indicate a reduction in the fair value of the IPR&D assets below their respective carrying amounts. If and when development is complete, which generally occurs if and when regulatory approval to market a product is obtained, the associated assets would be deemed finite-lived and would then be amortized based on their respective estimated useful lives at that point in time.
	See Note 6 to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 for additional information related to the Company’s Intangible Assets.

PROPERTY_PLANT_AND_EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	3 Months Ended
	Mar. 31, 2015
Property Plant And Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	(11) PROPERTY, PLANT AND EQUIPMENT
	Property, plant and equipment, net consisted of the following:
		March 31,			December 31,
		2015			2014
	Leasehold improvements	$	40,733		$	39,297
	Building and improvements		339,161			335,991
	Manufacturing and laboratory equipment		129,348			124,564
	Computer hardware and software		99,879			97,032
	Furniture and equipment		14,874			13,717
	Land improvements		4,106			4,106
	Land		29,357			29,358
	Construction-in-progress		120,971			108,340
			778,429			752,405
	Less: Accumulated depreciation		(240,312	)		(228,889	)
	Total property, plant and equipment, net	$	538,117		$	523,516
	Depreciation expense for the three months ended March 31, 2015 and 2014 was $11.5 million and $9.6 million, respectively, of which $3.6 million and $2.9 million, respectively, was capitalized into inventory.
	Capitalized interest related to the Company’s property, plant and equipment purchases for each of the three months ended March 31, 2015 and 2014 was insignificant.

SUPPLEMENTAL_BALANCE_SHEET_INF

SUPPLEMENTAL BALANCE SHEET INFORMATION	3 Months Ended
	Mar. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
SUPPLEMENTAL BALANCE SHEET INFORMATION	(12) SUPPLEMENTAL BALANCE SHEET INFORMATION
	Inventory consisted of the following:
		March 31,		December 31,
		2015		2014
	Raw materials	$	21,690	$	22,488
	Work-in-process		124,192		114,393
	Finished goods		76,951		62,571
	Total inventory	$	222,833	$	199,452
	Other Current Assets consisted of the following:
		March 31,		December 31,
		2015		2014
	Prepaid expenses		39,159		35,390
	Short-term forward currency exchange contract assets		18,337		10,513
	Promissory notes receivable, net		3,326		46,946
	Restricted investments		7,131		2,354
	Convertible promissory note conversion option		—		2,386
	Other receivables		10,983		9,733
	Other		5,329		4,513
	Total other current assets	$	84,265	$	111,835
	Other Assets consisted of the following:
		March 31,		December 31,
		2015		2014
	Deposits		11,045		12,021
	Deferred debt offering costs		10,911		11,763
	Strategic investments		44,918		30,811
	Long-term forward foreign currency exchange contract assets		7,391		5,387
	Other		6,067		5,299
	Total other assets	$	80,332	$	65,281
	Accounts payable and accrued liabilities consisted of the following:
		March 31,		December 31,
		2015		2014
	Accounts payable	$	23,606	$	32,779
	Accrued accounts payable		106,462		98,490
	Accrued compensation expense		32,461		45,479
	Accrued vacation expense		15,871		12,540
	Accrued rebates payable		17,173		14,859
	Accrued royalties payable		7,207		9,050
	Value added taxes payable		5,730		5,479
	Other accrued operating expenses		8,721		8,244
	Other		12,981		4,924
	Total accounts payable and accrued liabilities	$	230,212	$	231,844

CONVERTIBLE_DEBT

CONVERTIBLE DEBT	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
CONVERTIBLE DEBT	(13) CONVERTIBLE DEBT
	The following table summarizes information regarding the Company’s convertible debt:
			31-Mar-15		31-Dec-14
	Convertible Notes due 2020, net of unamortized discount of		$	300,786	$	297,955
	$74,214 and $77,045, at March 31, 2015 and
	December 31, 2014, respectively
	Convertible Notes due 2018, net of unamortized discount of			322,807		319,463
	$52,193 and $55,537, at March 31, 2015 and
	December 31, 2014, respectively
	Convertible Notes due 2017			31,898		40,558
	Total convertible debt, net of unamortized discount		$	655,491	$	657,976
	Fair value of fixed rate convertible debt
	Convertible Notes due in 2020 (1)		$	568,444	$	456,360
	Convertible Notes due in 2018 (1)			555,994		442,448
	Convertible Notes due in 2017 (1)			195,370		180,984
	Total		$	1,319,808	$	1,079,792
	-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.
	Interest expense on the Company’s convertible debt was comprised of the following:
			Three Months Ended March 31,
			2015		2014
	Coupon interest		$	2,462	$	2,408
	Amortization of issuance costs			826		843
	Accretion of debt discount			6,174		5,855
	Total interest expense on convertible debt		$	9,462	$	9,106
	During the three months ended March 31, 2015, the Company entered into separate agreements with three existing holders of its senior subordinated convertible notes due in 2017 (the 2017 Notes) pursuant to which such holders converted $8.1 million in aggregate principal amount of the 2017 Notes into 399,469 shares of the Company’s common stock. In addition to issuing the requisite number of shares of the Company’s common stock, the Company also made varying cash payments to the holder totaling $0.2 million in aggregate, of which $0.2 million was recognized in total as Debt Conversion Expense on the Condensed Consolidated Statement of Comprehensive Loss for the three months ended March 31, 2015.
	See Note 13 to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 for additional information related to the Company’s Convertible Debt.

DERIVATIVE_INSTRUMENTS_AND_HED

DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES	3 Months Ended
	Mar. 31, 2015
Derivative Instruments And Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES	(14) DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES
	The Company uses forward foreign currency exchange contracts to hedge certain operational exposures resulting from potential changes in foreign currency exchange rates. Such exposures result from portions of the Company’s forecasted revenues and operating expenses being denominated in currencies other than the U.S. dollar, primarily the Euro, the British Pound and the Brazilian Real.
	The Company designates certain of these forward foreign currency exchange contracts as hedging instruments and enters into some forward foreign currency exchange contracts that are considered to be economic hedges that are not designated as hedging instruments. Whether designated or undesignated, these forward foreign currency exchange contracts protect against the reduction in value of forecasted foreign currency cash flows resulting from product revenues, royalty revenues, operating expenses and asset or liability positions designated in currencies other than the U.S. dollar. The fair values of forward foreign currency exchange contracts are estimated using current exchange rates and interest rates, and take into consideration the current creditworthiness of the counterparties or the Company, as applicable. Details of the specific instruments used by the Company to hedge its exposure to foreign currency exchange rate fluctuations are discussed below. See Note 15 to these Condensed Consolidated Financial Statements for additional discussion regarding the fair value of forward foreign currency exchange contracts.
	At March 31, 2015, the Company had 94 forward foreign currency exchange contracts outstanding to sell a total of 131.6 million Euros and seven forward foreign currency exchange contracts outstanding to purchase 20.0 million Euros with expiration dates ranging from April 2015 through March 2018. These hedges were entered into in order to protect against the fluctuations in revenue associated with Euro-denominated product sales and operating expenses. The Company has formally designated these forward foreign currency exchange contracts as cash flow hedges and expects them to be highly effective in offsetting fluctuations in revenues denominated in Euros related to changes in foreign currency exchange rates.
	The Company also enters into forward foreign currency exchange contracts that are not designated as hedges for accounting purposes. The changes in fair value of these forward foreign currency exchange contracts are included as a part of SG&A expense in the Company’s Condensed Consolidated Statements of Comprehensive Loss. At March 31, 2015, the Company had one outstanding forward foreign currency exchange contract to sell 42.1 million Euros and one outstanding forward foreign currency exchange contract to sell 6.4 million British Pounds, both of which were not designated as a hedge for accounting purposes and matured on April 30, 2015.
	The maximum length of time over which the Company is hedging its exposure to the reduction in value of forecasted foreign currency revenues through forward foreign currency exchange contracts is through March 2018. Over the next twelve months, the Company expects to reclassify $18.9 million from accumulated other comprehensive income to earnings as the forecasted revenue transactions occur.
	The fair value carrying amounts of the Company’s derivative instruments were as follows:
			Asset Derivatives						Liability Derivatives
			31-Mar-15						31-Mar-15
			Balance Sheet Location		Fair Value				Balance Sheet Location	Fair Value
	Derivatives designated as hedging instruments:
	Forward foreign currency exchange contracts		Other current assets		$	18,171			Accounts payable and accrued liabilities	$	—
	Forward foreign currency exchange contracts		Other assets			7,391			Other long- term liabilities		—
	Total				$	25,562				$	—
	Derivatives not designated as hedging
	instruments:
	Forward foreign currency exchange contracts		Other current assets		$	166			Other long- term liabilities	$	805
	Total					166					805
	Total value of derivative contracts				$	25,728				$	805
			Asset Derivatives						Liability Derivatives
			31-Dec-14						31-Dec-14
			Balance Sheet Location		Fair Value				Balance Sheet Location	Fair Value
	Derivatives designated as hedging instruments:
	Forward foreign currency exchange contracts		Other current assets		$	10,206			Accounts payable and accrued liabilities	$	—
	Forward foreign currency exchange contracts		Other assets			5,387			Other long- term liabilities		—
	Total				$	15,593				$	—
	Derivatives not designated as hedging
	instruments:
	Forward foreign currency exchange contracts		Other current assets		$	307			Accounts payable and accrued liabilities	$	12
	Total					307					12
	Total value of derivative contracts				$	15,900				$	12
	The effect of the Company’s derivative instruments on the Condensed Consolidated Financial Statements for the three months ended March 31, 2015 and 2014 was as follows:
			Forward Foreign Currency Exchange Contracts
			Three Months Ended March 31,
			2015				2014
	Derivatives Designated as Hedging Instruments:
	Net gain recognized in Other Comprehensive Income (OCI) (1)		$	13,776			$	1,396
	Net gain reclassified from accumulated OCI into income (2)			4,739				(567	)
	Net gain (loss) recognized in net loss (3)			141				(121	)
	Derivatives Not Designated as Hedging Instruments:
	Net gain recognized in net loss(4)		$	7,800			$	56
	-1	Net change in the fair value of the effective portion classified as OCI.
	-2	Effective portion classified as net product revenue.
	-3	Ineffective portion and amount excluded from effectiveness testing classified as SG&A expense.
	-4	Classified as SG&A expense.
	At March 31, 2015 and December 31, 2014, accumulated other comprehensive income before taxes associated with forward foreign currency exchange contracts qualifying for hedge accounting treatment was a gain of $24.5 million and a gain of $15.9 million, respectively.
	The Company is exposed to counterparty credit risk on all of its derivative financial instruments. The Company has established and maintains strict counterparty credit guidelines and enters into hedges only with financial institutions that are investment grade or better to minimize the Company’s exposure to potential defaults. The Company does not require collateral to be pledged under these agreements.

FAIR_VALUE_MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	(15) FAIR VALUE MEASUREMENTS
	The Company measures certain financial assets and liabilities at fair value on a recurring basis, including available-for-sale fixed income securities and foreign currency derivatives. The tables below present the fair value of these financial assets and liabilities determined using the following input levels.
			Fair Value Measurements at March 31, 2015
			Quoted Price in		Significant Other		Significant		Total
			Active Markets		Observable		Unobservable
			For Identical		Inputs		Inputs
			Assets		(Level 2)		(Level 3)
			(Level 1)
	Assets:
	Cash and cash equivalents:
	Overnight deposits		$	833,545	$	—	$	—	$	833,545
	Money market instruments			—		67,025		—		67,025
	Total cash and cash equivalents			833,545		67,025		—		900,570
	Available-for-sale securities:
	Short-term:
	Certificates of deposit			—		57,176		—		57,176
	Corporate debt securities			—		15,546		—		15,546
	Commercial paper			—		21,354		—		21,354
	U.S. government agency securities			—		14,043		—		14,043
	Long-term:
	Certificates of deposit			—		12,696		—		12,696
	Corporate debt securities			—		132,120		—		132,120
	U.S. government agency securities			—		79,000		—		79,000
	Greek government-issued bonds			—		104		—		104
	Total available-for-sale securities			—		332,039		—		332,039
	Other Current Assets:
	Nonqualified Deferred Compensation Plan assets			—		353		—		353
	Forward foreign currency exchange contract(1)			—		18,337		—		18,337
	Restricted investments (2)			—		7,131		—		7,131
	Total other current assets			—		25,821		—		25,821
	Other Assets:
	Nonqualified Deferred Compensation Plan assets			—		5,884		—		5,884
	Forward foreign currency exchange contract(1)			—		7,391		—		7,391
	Strategic investment (4)			41,809		—		—		41,809
	Total other assets			41,809		13,275		—		55,084
	Total assets		$	875,354	$	438,160	$	—	$	1,313,514
	Liabilities:
	Current Liabilities:
	Nonqualified Deferred Compensation Plan liability		$	1,198	$	353	$	—	$	1,551
	Contingent acquisition consideration payable			—		—		75,294		75,294
	Total current liabilities			1,198		353		75,294		76,845
	Other long-term liabilities:
	Nonqualified Deferred Compensation Plan liability			25,402		5,884		—		31,286
	Forward foreign currency exchange contract (1)			—		805		—		805
	Contingent acquisition consideration payable			—		—		39,052		39,052
	Total other long-term liabilities			25,402		6,689		39,052		71,143
	Total liabilities		$	26,600	$	7,042	$	114,346	$	147,988
			Fair Value Measurements at December 31, 2014
			Quoted Price in		Significant Other		Significant		Total
			Active Markets		Observable		Unobservable
			For Identical		Inputs		Inputs
			Assets		(Level 2)		(Level 3)
			(Level 1)
	Assets:
	Cash and cash equivalents:
	Overnight deposits		$	225,159	$	—	$	—	$	225,159
	Money market instruments			—		650,327		—		650,327
	Total cash and cash equivalents			225,159		650,327		—		875,486
	Available-for-sale securities:
	Short-term:
	Certificates of deposit			—		54,174		—		54,174
	Corporate debt securities			—		15,532		—		15,532
	Long-term:
	Certificates of deposit			—		18,129		—		18,129
Corporate debt securities			—		79,604		—		79,604
Greek government-issued bonds			—		123		—		123
Total available-for-sale securities			—		167,562		—		167,562
Other Current Assets:
Nonqualified Deferred Compensation Plan assets			—		514		—		514
Forward foreign currency exchange contract(1)			—		10,513		—		10,513
Restricted investments (2)			—		2,354		—		2,354
Embedded derivative (3)			—		—		2,386		2,386
Total other current assets			—		13,381		2,386		15,767
Other Assets:
Nonqualified Deferred Compensation Plan assets			—		5,112		—		5,112
Restricted investments (2)			—		5,387		—		5,387
Strategic investment (4)			30,811		—		—		30,811
Total other assets			30,811		10,499		—		41,310
Total assets		$	255,970	$	841,769	$	2,386	$	1,100,125
Liabilities:
Current Liabilities:
Nonqualified Deferred Compensation Plan liability		$	1,790	$	514	$	—	$	2,304
Forward foreign currency exchange contract(1)			—		12		—		12
Contingent acquisition consideration payable			—		—		3,895		3,895
Total current liabilities			1,790		526		3,895		6,211
Other long-term liabilities:
Nonqualified Deferred Compensation Plan liability			18,453		5,112		—		23,565
Contingent acquisition consideration payable			—		—		38,767		38,767
Total other long-term liabilities			18,453		5,112		38,767		62,332
Total liabilities		$	20,243	$	5,638	$	42,662	$	68,543
-1	See Note 14 to these Condensed Consolidated Financial Statements for further information regarding the derivative instruments.
-2	The restricted investments at March 31, 2015 and December 31, 2014 secure the Company’s irrevocable standby letter of credit obtained in connection with certain commercial agreements.
-3	The embedded derivative at December 31, 2014 represents the fair value of the conversion feature of a promissory note which may be settled in the issuer’s underlying shares.
-4	The Company has investments in marketable equity securities measured using quoted prices in an active market that are considered strategic investments. See Note 8 to these Condensed Consolidated Financial Statements for additional discussion regarding the Company’s strategic investments.
There were no transfers between levels during the three months ended March 31, 2015.
The Company’s Level 2 securities are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads, benchmark securities, prepayment/default projections based on historical data and other observable inputs.
The Company validates the prices provided by its third-party pricing services by understanding the models used, obtaining market values from other pricing sources, analyzing pricing data in certain instances and confirming those securities traded in active markets. See Note 8 to these Condensed Consolidated Financial Statements for further information regarding the Company’s financial instruments.
Liabilities measured at fair value using Level 3 inputs were comprised of contingent acquisition consideration payable and asset retirement obligations.
The Company’s contingent acquisition consideration payable is estimated using a probability-based income approach utilizing an appropriate discount rate. Key assumptions used by management to estimate the fair value of contingent acquisition consideration payable include estimated probabilities, the estimated timing of when a milestone may be attained and assumed discount periods and rates. Subsequent changes in the fair value of the contingent acquisition consideration payable, resulting from management’s revision of key assumptions, will be recorded in Intangible Asset Amortization and Contingent Consideration in the Company’s Condensed Consolidated Statements of Comprehensive Loss. The probability-based income approach used by management to estimate the fair value of the contingent acquisition consideration is most sensitive to changes in the estimated probabilities.
Contingent acquisition consideration payable at December 31, 2014		$	42,662
Addition of contingent consideration payable related to			71,402
the Prosensa acquisition (CVR)
Changes in the fair value of the contingent acquisition			282
consideration payable
Contingent acquisition consideration payable at March 31, 2015		$	114,346
Under certain of the Company’s lease agreements, the Company is contractually obligated to return leased space to its original condition upon termination of the lease agreement. The Company records an asset retirement obligation liability and a corresponding capital asset in an amount equal to the estimated fair value of the obligation when estimable. In subsequent periods, for each such lease, the Company records Interest Expense to accrete the asset retirement obligation liability to full value and depreciates each capitalized asset retirement obligation asset, both over the term of the associated lease agreement.
Asset retirement obligations at December 31, 2014		$	3,765
Accretion expense			36
Additions			84
Asset retirement obligations at March 31, 2015		$	3,885
The Company acquired intangible assets as a result of various business acquisitions. The estimated fair value of these long-lived assets was measured using Level 3 inputs as of the acquisition date.

STOCKBASED_COMPENSATION

STOCK-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
STOCK-BASED COMPENSATION	(16) STOCK-BASED COMPENSATION
	The Company’s stock-based compensation plans include the Amended and Restated 2006 Share Incentive Plan (the Share Incentive Plan), the ESPP, the 2014 Inducement Plan and the 2012 Inducement Plan. The 2012 Inducement Plan expired in May 2013. The Company’s stock-based compensation plans are administered by the Compensation Committee of the Board of Directors, which selects persons to receive awards and determines the number of shares subject to each award and the terms, conditions, performance measures and other provisions of the award. See Note 16 to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014, for additional information related to these stock-based compensation plans.
	Determining the Fair Value of Stock Options and Stock Purchase Rights
	The fair value of each option award is estimated on the date of grant using the Black-Scholes valuation model and the assumptions noted in the tables below. The expected life of options is based on observed historical exercise patterns. Groups of employees that have similar historical exercise patterns were considered separately for valuation purposes, but none were identified that had distinctly different exercise patterns as of March 31, 2015. The expected volatility of stock options is based upon the weighted average of the historical volatility of the Company’s common stock and the implied volatility of traded options on the Company’s common stock for fiscal periods in which there is sufficient trading volume in options on the Company’s common stock. The risk-free interest rate is based on the implied yield on a U.S. Treasury zero-coupon issue with a remaining term equal to the expected term of the option. The dividend yield reflects that the Company has not paid any cash dividends since inception and does not intend to pay any cash dividends in the foreseeable future. The assumptions used to estimate the per share fair value of stock options granted under the 2012 Inducement Plan and 2014 Inducement Plan and the Share Incentive Plan were as follows:
		Three Months Ended March 31,
		2015		2014
	Expected volatility	44 – 45%		44 – 45%
	Dividend yield		0.00%		0.00%
	Expected life	7.0 years		6.9 years
	Risk-free interest rate	1.5 – 2.0%		2.1 – 2.3%
	During the three months ended March 31, 2015, the Company granted 642,070 options with a weighted average fair value of $56.11 per option.
	The Company did not issue any new stock purchase rights under the ESPP during the three months ended March 31, 2015.
	Restricted Stock Unit Awards with Service-Based Vesting Conditions
	Restricted stock units (RSUs) are generally subject to forfeiture if employment terminates prior to the release of vesting restrictions. The Company expenses the cost of the RSUs, which is determined to be the fair market value of the shares of common stock underlying the RSUs at the date of grant, ratably over the period during which the vesting restrictions lapse. During the three months ended March 31, 2015, the Company granted 825,900 RSUs with a weighted average fair market value of $120.95 per share.
	Restricted Stock Unit Awards with Performance and Market-Based Vesting Conditions
	During 2012 and 2011, pursuant to the approval of the Board of Directors (the Board), the Company granted 860,000 RSU awards with performance and market-based vesting conditions (the 2011/2012 Base RSUs) under the Share Incentive Plan and the 2012 Inducement Plan to certain executive officers. As of March 31, 2015, the 2011/2012 Base RSUs had a weighted-average grant date fair value of $34.66. The 2011/2012 Base RSUs will vest upon the achievement of specific performance goals (the Earned RSUs). The number of RSUs that will be awarded from the Earned RSUs will be calculated by multiplying the Earned RSUs by the Total Shareholder Return multiplier which could range from 75% to 125%.
	Stock-based compensation expense for this award will be recognized over the remaining service period beginning in the period the Company determines the strategic performance goal or goals is probable of achievement. During the fourth quarter of 2014, management concluded that the achievement of the 2015 revenue performance goal was probable and began recognizing compensation expense related to the RSUs allocated to the revenue performance goal. During 2013, management concluded that regulatory approval of Vimizim was probable and began recognizing compensation expense related to the performance 2011/2012 Base RSUs allocated to the Vimizim performance goal. For the three months ended March 31, 2015 and 2014, the Company recorded $1.8 million and $0.6 million, respectively, of compensation expense related to these performance awards.
	Restricted Stock Unit Awards with Performance Conditions
	On March 3, 2015, pursuant to Board approval, the Company granted 58,300 RSU awards with performance-vesting conditions (the 2015 Base RSUs) under the Share Incentive Plan to certain executive officers. The vesting of the 2015 Base RSUs under this specific grant is contingent upon the achievement of a 2015 revenue target and a three-year service period. The number of RSUs that will be awarded from the 2015 Base RSUs upon achievement of the performance condition will be calculated by multiplying the 2015 Base RSUs by a revenue multiplier (determined based on the Company’s performance against the revenue target) which could range between 80% or 120%. The maximum number of RSUs that could vest if the performance condition is achieved and a revenue multiplier of 120% is applied is 69,960.
	Stock-based compensation for these awards will be recognized over the service period beginning in the period the Company determines it is probable that the revenue target will be achieved. The cost of the 2015 Base RSUs was determined to be $108.36 per RSU, based on the fair value of the common stock underlying the 2015 Base RSUs on the grant date. Accordingly, because the Company’s management determined that attainment of the revenue target was probable as of March 31, 2015, the Company recognized $0.2 million of compensation expense related to this awards during the three months ended March 31, 2015.
	Compensation expense included in the Company’s Condensed Consolidated Statements of Comprehensive Loss for all stock-based compensation arrangements was as follows:
		Three Months Ended March 31,
		2015		2014
	Cost of sales	$	1,348	$	1,086
	R&D		9,930		7,115
	SG&A		11,414		8,103
	Total stock-based compensation expense	$	22,692	$	16,304
	Stock-based compensation of $2.5 million and $2.1 million was capitalized into inventory, for the three months ended March 31, 2015 and 2014, respectively. Capitalized stock-based compensation is recognized as cost of sales when the related product is sold.

COMPREHENSIVE_LOSS

COMPREHENSIVE LOSS	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
COMPREHENSIVE LOSS	(17) COMPREHENSIVE LOSS
	The following table summarizes amounts reclassified out of Accumulated Other Comprehensive Income/(Loss) (AOCI) and their effect on the Company’s Condensed Consolidated Statements of Comprehensive Loss for the three months ended March 31, 2015 and 2014.
		Amount Reclassified from
		AOCI Gain (Loss)
		Three Months Ended March 31,						Consolidated Statement of
	Details about AOCI Components	2015			2014			Operations Classification
	Gains (loss) on cash flow hedges:
	Forward foreign currency exchange contracts	$	4,739		$	(887	)	Net product revenues
			—			320		Provision for income taxes
		$	4,739		$	(567	)	Net loss
	The following table summarizes changes in the accumulated balances for each component of AOCI, including current period other comprehensive income and reclassifications out of AOCI, for the three months ended March 31, 2015 and 2014.
		Three Months Ended March 31, 2015
		Before Tax			Tax (Expense)			Net-of-Tax
		Amount			Benefit			Amount
	AOCI balance at December 31, 2014	$	33,984		$	(6,518	)	$	27,466
	Foreign currency translation adjustment		(5	)		—			(5	)
	Unrealized gain on available-for-sale securities:
	Unrealized holding gains		11,481			(4,160	)		7,321
	Less: reclassification adjustment for gain realized in net		—			—			—
	loss
	Net unrealized holding gain		11,481			(4,160	)		7,321
	Net unrealized holding gain on cash flow hedges:
	Unrealized holding gain		13,776			—			13,776
	Less: reclassification adjustment for gain realized in net		4,739			—			4,739
	loss
	Net unrealized holding gain		9,037			—			9,037
	Other comprehensive income		20,513			(4,160	)		16,353
	AOCI balance at March 31, 2015	$	54,497		$	(10,678	)	$	43,819
		Three Months Ended March 31, 2014
		Before Tax			Tax (Expense)			Net-of-Tax
		Amount			Benefit			Amount
	AOCI balance at December 31, 2013	$	7,756		$	(2,738	)	$	5,018
	Foreign currency translation adjustment		5			—			5
	Unrealized gain on available-for-sale securities:
	Unrealized holding gains		2,244			(821	)		1,423
	Less: reclassification adjustment for gain realized in net		—			—			—
	loss
	Net unrealized holding gain		2,244			(821	)		1,423
	Net unrealized holding gain on cash flow hedges:
	Unrealized holding gain		2,183			(787	)		1,396
	Less: reclassification adjustment for loss realized in net		(887	)		320			(567	)
	loss
	Net unrealized holding gain		1,296			(467	)		829
	Other comprehensive income		3,545			(1,288	)		2,257
	AOCI balance at March 31, 2014	$	11,301		$	(4,026	)	$	7,275

REVENUE_AND_CREDIT_CONCENTRATI

REVENUE AND CREDIT CONCENTRATIONS	3 Months Ended
	Mar. 31, 2015
Risks And Uncertainties [Abstract]
REVENUE AND CREDIT CONCENTRATIONS	(18) REVENUE AND CREDIT CONCENTRATIONS
	Net Product Revenue—The Company considers there to be revenue concentration risks for regions where net product revenue exceeds ten percent (10%) of consolidated net product revenue. The concentration of the Company’s net product revenue within the regions below may have a material adverse effect on the Company’s revenue and results of operations if sales in the respective regions experience difficulties.
	The table below summarizes consolidated net product revenue concentrations based on patient location for Vimizim, Naglazyme, Kuvan and Firdapse and the headquarters for Genzyme Corporation (Genzyme) for Aldurazyme. Although Genzyme sells Aldurazyme worldwide, the royalties earned by the Company on Genzyme’s net sales are included in the U.S. region, as the transactions are with Genzyme whose headquarters are located in the U.S.
			Three Months Ended March 31,
			2015			2014
	Region:
	United States			44	%		47	%
	Europe			21	%		20	%
	Latin America			17	%		16	%
	Rest of world			18	%		17	%
	Total net product revenue			100	%		100	%
	The following table illustrates the percentage of the Company’s consolidated net product revenue attributed to the Company’s four largest customers.
			Three Months Ended March 31,
			2015			2014
	Customer A			15	%		16	%
	Customer B (1)			9	%		12	%
	Customer C			11	%		11	%
	Customer D			12	%		11	%
	Total			47	%		50	%
	-1	Genzyme is the Company’s sole customer for Aldurazyme and is responsible for marketing and selling Aldurazyme to third-parties. Net product revenues from Genzyme are comprised of royalties on worldwide net Aldurazyme sales and incremental product transfer revenue.
	On a consolidated basis, the Company’s two largest customers accounted for 29% and 21% of the March 31, 2015 accounts receivable balance, respectively, compared to December 31, 2014 when the two largest customers accounted for 42% and 18% of the accounts receivable balance, respectively. As of March 31, 2015 and December 31, 2014, accounts receivable for the Company’s largest customer balance included $30.2 million and $34.5 million, respectively, of unbilled accounts receivable related to net incremental Aldurazyme product transfers to 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 is subject to credit risk from accounts receivable related to product sales. The majority of the Company’s trade accounts receivable arises from product sales in the U.S. and the EU. The Company’s product sales to government-owned or government-funded customers in certain European countries, including Italy, Spain, Portugal, Greece and Russia, are subject to payment terms that are statutorily determined. Because these customers are government-owned or government-funded, the Company may be impacted by declines in sovereign credit ratings or sovereign defaults in these countries. A significant or further decline in sovereign credit ratings or a default in these countries may decrease the likelihood that the Company will collect accounts receivable or may increase the discount rates and the length of time until receivables are collected, which could result in a negative impact to the Company’s operating results. In the three months ended March 31, 2015, the Company’s net product revenues for these countries was 4%. Additionally, approximately 7% of the Company’s outstanding accounts receivable at March 31, 2015 related to such countries.
	As of March 31, 2015, the Company’s accounts receivable in certain European countries, specifically Greece, Italy, Portugal, Spain and Russia, totaled approximately $12.0 million, of which $0.8 million was greater than 90 days past due, $0.4 million was greater than 180 days past due and $0.1 was greater than 365 days past due.
	The Company also sells its products in other countries that face economic crises and local currency devaluation. Although the Company has historically collected receivables from customers in those 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. The Company believes that the allowances for doubtful accounts related to these countries is adequate based on its analysis of the specific business circumstances and expectations of collection for each of the underlying accounts in these countries.

SEGMENT_INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
SEGMENT INFORMATION	(19) SEGMENT INFORMATION
	The Company operates in one business segment, which primarily focuses on the development and commercialization of innovative biopharmaceuticals for serious diseases and medical conditions. All products are included in one segment because the majority of our products have similar economic and other characteristics, including the nature of the products and production processes, type of customers, distribution methods and regulatory environment.
		Three Months Ended March 31,
		2015		2014
	Net product revenue by product:
	Vimizim	$	50,622	$	875
	Naglazyme		78,167		80,114
	Kuvan		50,193		45,236
	Aldurazyme		18,243		18,070
	Firdapse		4,087		4,709
	Total net product revenue	$	201,312	$	149,004
	Net product revenue is based on patient location for Vimizim, Naglazyme, Kuvan and Firdapse and Genzyme’s headquarters for Aldurazyme. Although Genzyme sells Aldurazyme worldwide, the royalties earned by the Company on Genzyme’s net sales are included in the U.S. region, as the transactions are with Genzyme whose headquarters are located in the U.S.
	The following table summarizes total revenues from external customers and collaborative partners by geographic region.
		Three Months Ended March 31,
		2015		2014
	Total revenues by geographic region:
	United States	$	90,592	$	71,649
	Europe		41,710		30,654
	Latin America		34,818		22,209
	Rest of world		36,144		27,040
	Total revenues	$	203,264	$	151,552

PROVISION_FOR_BENEFIT_FROM_INC

PROVISION FOR (BENEFIT FROM) INCOME TAXES	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
PROVISION FOR (BENEFIT FROM) INCOME TAXES	(20) PROVISION FOR (BENEFIT FROM) INCOME TAXES
	The Company has historically computed its interim period provision for (benefit from) income taxes by applying its forecasted effective tax rate to year-to-date earnings. However, due to a significant amount of U.S. permanent differences relative to the amount of U.S. forecasted income used in computing the effective tax rate, the effective tax rate is highly sensitive to minor fluctuations in U.S forecasted income. As such, the Company computed the U.S component of the consolidated provision for (benefit from) income taxes for the three months ended March 31, 2015 and 2014 using the actual year-to-date tax calculation. Foreign tax expense was computed using a forecasted annual effective tax rate for the three months ended March 31, 2015 and 2014.

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	(21) COMMITMENTS AND CONTINGENCIES
	Contingencies
	From time to time the Company is involved in legal actions arising in the normal course of its business. The most significant of these actions are described below.
	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.
	Paragraph IV Notices
	As previously disclosed, the Company received a paragraph IV notice letter, dated October 3, 2014, from Dr. Reddy’s Laboratories, Inc. and Dr. Reddy’s Laboratories, Ltd. (collectively, DRL), notifying the Company that DRL has filed an abbreviated new drug application (ANDA) seeking approval of a proposed generic version of Kuvan (sapropterin dihydrochloride) 100 mg oral tablets prior to the expiration of the Company’s patents listed in the U.S. Food and Drug Administration’s (the FDA) Approved Drug Products with Therapeutic Equivalence Evaluations (the Orange Book).  Additionally, the Company received a paragraph IV notice letter, dated January 22, 2015, from Par Pharmaceutical, Inc. (Par), notifying the Company that Par has filed an ANDA seeking approval of a proposed generic version of Kuvan (sapropterin dihydrochloride) 100 mg oral tablets prior to the expiration of the Company’s patents listed in the FDA’s Orange Book.  Together with Merck & Cie (Merck), the Company filed lawsuits against both DRL and Par in the United States District Court for the District of New Jersey alleging patent infringement for the Company’s patents relating to Kuvan triggering the automatic 30 month stay on the approval of each ANDA.
	Contingent Payments
	As of March 31, 2015, the Company is subject to contingent payments totaling approximately $733.4 million upon achievement of certain regulatory and licensing milestones if they occur before certain dates in the future. Of this amount, $51.4 million relates to programs that are no longer being developed.
	As of March 31, 2015, the Company has recorded $114.3 million of contingent acquisition consideration payable on its Condensed Consolidated Balance Sheet, of which $75.3 million is expected to be paid in the next twelve months.
	In the normal course of business, the Company enters into various firm purchase commitments primarily related to research and development and certain inventory related items. As of March 31, 2015, these commitments for the next five years were approximately $74.0 million. These amounts primarily relate to active pharmaceutical ingredients and represent minimum purchase requirements and post marketing commitments related to the Company’s approved products.

SIGNIFICANT_ACCOUNTING_POLICIE1

SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Reclassifications	Reclassifications
	Certain items in the Company’s prior year Condensed Consolidated Financial Statements have been reclassified to conform to the current presentation.

ACQUISITIONS_Tables

ACQUISITIONS (Tables)	3 Months Ended
	Mar. 31, 2015
Business Acquisition [Line Items]
Fair Value of Identifiable Intangible Assets Acquired by Asset Class	The following table sets forth the fair value of the components of the identifiable intangible assets acquired by asset class as of the date of acquisition:
	Above market leases	$	351
	In-place leases		3,554
	Total intangible assets subject to amortization	$	3,905
Prosensa Holding N.V
Business Acquisition [Line Items]
Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed	The following table presents the allocation of the purchase consideration for the Prosensa acquisition, including the CVRs, based on fair value.
	Cash and cash equivalents	$	141,669
	Trade accounts receivable		3,086
	Other current assets		1,537
	Property, plant and equipment		2,683
	Intangible assets		497
	Other assets		104
	Acquired IPR&D		772,808
	Total identifiable assets acquired		922,384
	Accounts payable and accrued expenses		(68,799	)
	Debt assumed		(57,053	)
	Deferred tax liability		(193,202	)
	Total liabilities assumed		(319,054	)
	Net identifiable assets acquired		603,330
	Goodwill		148,134
	Net assets acquired	$	751,464
San Rafael Corporate Center
Business Acquisition [Line Items]
Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed	The following table summarizes the estimated fair values of assets acquired as of the date of acquisition:
		Estimated			Estimated
		Fair Value			Useful Lives
	Building and improvements	$	94,414		50 years
	Land		14,565
	Land improvements		3,616		10 years
	Intangible assets		3,905		Remaining
					lease terms
	Total identifiable net assets	$	116,500

NET_LOSS_PER_COMMON_SHARE_Tabl

NET LOSS PER COMMON SHARE (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings per Common Share	The following table sets forth the computation of basic and diluted earnings per common share (in thousands of common shares):
		Three Months Ended March 31,
		2015			2014
	Numerator:
	Net loss, basic	$	(67,501	)	$	(38,115	)
	Gain on Company common stock issued to the NQDC		—			(374	)
	Net loss, diluted	$	(67,501	)	$	(38,489	)
	Denominator:
	Weighted-average common shares outstanding, basic		157,612			143,983
	Effect of dilutive securities:
	Common stock issued to the NQDC		—			174
	Weighted-average common shares outstanding, diluted		157,612			144,157
	Net loss per common share, basic	$	(0.43	)	$	(0.26	)
	Net loss per common share, diluted	$	(0.43	)	$	(0.27	)
Schedule Of Anti-Dilutive Common Stock Excluded From Computation of Diluted Net Loss Per Share	the table below presents potential shares of common stock that were excluded from the computation as they were anti-dilutive using the treasury stock method (in thousands of common shares):
		Three Months Ended March 31,
		2015			2014
	Options to purchase common stock		11,109			12,444
	Common stock issuable under the 2017 Notes		1,567			3,047
	Common stock issuable under the 2018 and 2020 Notes		7,966			7,966
	Unvested restricted stock units		1,557			1,326
	Potentially issuable common stock for ESPP purchases		223			209
	Common stock held by the NQDC		213			—
	Total number of potentially issuable shares		22,635			24,992

INVESTMENTS_Tables

INVESTMENTS (Tables)	3 Months Ended
	Mar. 31, 2015
Investments Schedule [Abstract]
Amortized Cost, Gross Unrealized Holding Gain or Loss, and Fair Value of Available For Sale Security by Major Security type	The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale securities by major security type at March 31, 2015 and December 31, 2014 are summarized in the tables below:
		Amortized Cost		Gross		Gross			Aggregate Fair
				Unrealized		Unrealized			Value at March 31, 2015
				Holding Gains		Holding Losses
	Certificates of deposit	$	69,871	$	1	$	—		$	69,872
	Corporate debt securities		147,537		129		—			147,666
	Commercial paper		21,354		—		—			21,354
	U.S. government agency securities		93,012		31		—			93,043
	Greek government-issued bonds		50		54		—			104
	Total	$	331,824	$	215	$	—		$	332,039
		Amortized Cost		Gross		Gross			Aggregate Fair
				Unrealized		Unrealized			Value at
				Holding Gains		Holding Losses			31-Dec-14
	Certificates of deposit	$	72,302	$	1	$	—		$	72,303
	Corporate debt securities		95,478		—		(342	)		95,136
	Greek government-issued bonds		50		73		—			123
	Total	$	167,830	$	74	$	(342	)	$	167,562
Fair Values of Available-For-Sale Securities by Contractual Maturity	The fair values of available-for-sale securities by contractual maturity were as follows:
		March 31,		December 31,
		2015		2014
	Maturing in one year or less	$	108,119	$	69,706
	Maturing after one year through five years		223,920		97,856
	Total	$	332,039	$	167,562

GOODWILL_SCHEDULE_OF_CHANGES_I

GOODWILL - SCHEDULE OF CHANGES IN GOODWILL (Tables)	3 Months Ended
	Mar. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Changes in Goodwill	The following table represents the changes in goodwill for the three months ended March 31, 2015:
	Balance at December 31, 2014	$	54,258
	Addition of goodwill related to the acquisition of Prosensa		148,134
	Balance at March 31, 2015	$	202,392

INTANGIBLE_ASSETS_Tables

INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Intangible assets consisted of the following:
		March 31,			December 31,
		2015			2014
	Intangible assets:
	Finite-lived intangible assets	$	123,836		$	123,365
	Indefinite-lived intangible assets		847,238			74,430
	Gross intangible assets:		971,074			197,795
	Less: Accumulated amortization		(44,178	)		(41,217	)
	Net carrying value	$	926,896		$	156,578

PROPERTY_PLANT_AND_EQUIPMENT_T

PROPERTY, PLANT AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2015
Property Plant And Equipment [Abstract]
Schedule of Property Plant and Equipment Net	Property, plant and equipment, net consisted of the following:
		March 31,			December 31,
		2015			2014
	Leasehold improvements	$	40,733		$	39,297
	Building and improvements		339,161			335,991
	Manufacturing and laboratory equipment		129,348			124,564
	Computer hardware and software		99,879			97,032
	Furniture and equipment		14,874			13,717
	Land improvements		4,106			4,106
	Land		29,357			29,358
	Construction-in-progress		120,971			108,340
			778,429			752,405
	Less: Accumulated depreciation		(240,312	)		(228,889	)
	Total property, plant and equipment, net	$	538,117		$	523,516

SUPPLEMENTAL_BALANCE_SHEET_INF1

SUPPLEMENTAL BALANCE SHEET INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule Of Inventory	Inventory consisted of the following:
		March 31,		December 31,
		2015		2014
	Raw materials	$	21,690	$	22,488
	Work-in-process		124,192		114,393
	Finished goods		76,951		62,571
	Total inventory	$	222,833	$	199,452
Schedule of Other Current Assets	Other Current Assets consisted of the following:
		March 31,		December 31,
		2015		2014
	Prepaid expenses		39,159		35,390
	Short-term forward currency exchange contract assets		18,337		10,513
	Promissory notes receivable, net		3,326		46,946
	Restricted investments		7,131		2,354
	Convertible promissory note conversion option		—		2,386
	Other receivables		10,983		9,733
	Other		5,329		4,513
	Total other current assets	$	84,265	$	111,835
Schedule of Other Assets	Other Assets consisted of the following:
		March 31,		December 31,
		2015		2014
	Deposits		11,045		12,021
	Deferred debt offering costs		10,911		11,763
	Strategic investments		44,918		30,811
	Long-term forward foreign currency exchange contract assets		7,391		5,387
	Other		6,067		5,299
	Total other assets	$	80,332	$	65,281
Schedule of Accounts Payable and Accrued Liabilities	Accounts payable and accrued liabilities consisted of the following:
		March 31,		December 31,
		2015		2014
	Accounts payable	$	23,606	$	32,779
	Accrued accounts payable		106,462		98,490
	Accrued compensation expense		32,461		45,479
	Accrued vacation expense		15,871		12,540
	Accrued rebates payable		17,173		14,859
	Accrued royalties payable		7,207		9,050
	Value added taxes payable		5,730		5,479
	Other accrued operating expenses		8,721		8,244
	Other		12,981		4,924
	Total accounts payable and accrued liabilities	$	230,212	$	231,844

CONVERTIBLE_DEBT_Tables

CONVERTIBLE DEBT (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Summary of Convertible Debt	The following table summarizes information regarding the Company’s convertible debt:
			31-Mar-15		31-Dec-14
	Convertible Notes due 2020, net of unamortized discount of		$	300,786	$	297,955
	$74,214 and $77,045, at March 31, 2015 and
	December 31, 2014, respectively
	Convertible Notes due 2018, net of unamortized discount of			322,807		319,463
	$52,193 and $55,537, at March 31, 2015 and
	December 31, 2014, respectively
	Convertible Notes due 2017			31,898		40,558
	Total convertible debt, net of unamortized discount		$	655,491	$	657,976
	Fair value of fixed rate convertible debt
	Convertible Notes due in 2020 (1)		$	568,444	$	456,360
	Convertible Notes due in 2018 (1)			555,994		442,448
	Convertible Notes due in 2017 (1)			195,370		180,984
	Total		$	1,319,808	$	1,079,792
	-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.
Summary of Convertible Debt Interest Expense	Interest expense on the Company’s convertible debt was comprised of the following:
			Three Months Ended March 31,
			2015		2014
	Coupon interest		$	2,462	$	2,408
	Amortization of issuance costs			826		843
	Accretion of debt discount			6,174		5,855
	Total interest expense on convertible debt		$	9,462	$	9,106

DERIVATIVE_INSTRUMENTS_AND_HED1

DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Fair Value Carrying Amount of Derivative Instruments	The fair value carrying amounts of the Company’s derivative instruments were as follows:
			Asset Derivatives						Liability Derivatives
			31-Mar-15						31-Mar-15
			Balance Sheet Location		Fair Value				Balance Sheet Location	Fair Value
	Derivatives designated as hedging instruments:
	Forward foreign currency exchange contracts		Other current assets		$	18,171			Accounts payable and accrued liabilities	$	—
	Forward foreign currency exchange contracts		Other assets			7,391			Other long- term liabilities		—
	Total				$	25,562				$	—
	Derivatives not designated as hedging
	instruments:
	Forward foreign currency exchange contracts		Other current assets		$	166			Other long- term liabilities	$	805
	Total					166					805
	Total value of derivative contracts				$	25,728				$	805
			Asset Derivatives						Liability Derivatives
			31-Dec-14						31-Dec-14
			Balance Sheet Location		Fair Value				Balance Sheet Location	Fair Value
	Derivatives designated as hedging instruments:
	Forward foreign currency exchange contracts		Other current assets		$	10,206			Accounts payable and accrued liabilities	$	—
	Forward foreign currency exchange contracts		Other assets			5,387			Other long- term liabilities		—
	Total				$	15,593				$	—
	Derivatives not designated as hedging
	instruments:
	Forward foreign currency exchange contracts		Other current assets		$	307			Accounts payable and accrued liabilities	$	12
	Total					307					12
	Total value of derivative contracts				$	15,900				$	12
Effect of Derivative Instruments	The effect of the Company’s derivative instruments on the Condensed Consolidated Financial Statements for the three months ended March 31, 2015 and 2014 was as follows:
			Forward Foreign Currency Exchange Contracts
			Three Months Ended March 31,
			2015				2014
	Derivatives Designated as Hedging Instruments:
	Net gain recognized in Other Comprehensive Income (OCI) (1)		$	13,776			$	1,396
	Net gain reclassified from accumulated OCI into income (2)			4,739				(567	)
	Net gain (loss) recognized in net loss (3)			141				(121	)
	Derivatives Not Designated as Hedging Instruments:
	Net gain recognized in net loss(4)		$	7,800			$	56
	-1	Net change in the fair value of the effective portion classified as OCI.
	-2	Effective portion classified as net product revenue.
	-3	Ineffective portion and amount excluded from effectiveness testing classified as SG&A expense.
	-4	Classified as SG&A expense.

FAIR_VALUE_MEASUREMENTS_Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	The Company measures certain financial assets and liabilities at fair value on a recurring basis, including available-for-sale fixed income securities and foreign currency derivatives. The tables below present the fair value of these financial assets and liabilities determined using the following input levels.
			Fair Value Measurements at March 31, 2015
			Quoted Price in		Significant Other		Significant		Total
			Active Markets		Observable		Unobservable
			For Identical		Inputs		Inputs
			Assets		(Level 2)		(Level 3)
			(Level 1)
	Assets:
	Cash and cash equivalents:
	Overnight deposits		$	833,545	$	—	$	—	$	833,545
	Money market instruments			—		67,025		—		67,025
	Total cash and cash equivalents			833,545		67,025		—		900,570
	Available-for-sale securities:
	Short-term:
	Certificates of deposit			—		57,176		—		57,176
	Corporate debt securities			—		15,546		—		15,546
	Commercial paper			—		21,354		—		21,354
	U.S. government agency securities			—		14,043		—		14,043
	Long-term:
	Certificates of deposit			—		12,696		—		12,696
	Corporate debt securities			—		132,120		—		132,120
	U.S. government agency securities			—		79,000		—		79,000
	Greek government-issued bonds			—		104		—		104
	Total available-for-sale securities			—		332,039		—		332,039
	Other Current Assets:
	Nonqualified Deferred Compensation Plan assets			—		353		—		353
	Forward foreign currency exchange contract(1)			—		18,337		—		18,337
	Restricted investments (2)			—		7,131		—		7,131
	Total other current assets			—		25,821		—		25,821
	Other Assets:
	Nonqualified Deferred Compensation Plan assets			—		5,884		—		5,884
	Forward foreign currency exchange contract(1)			—		7,391		—		7,391
	Strategic investment (4)			41,809		—		—		41,809
	Total other assets			41,809		13,275		—		55,084
	Total assets		$	875,354	$	438,160	$	—	$	1,313,514
	Liabilities:
	Current Liabilities:
	Nonqualified Deferred Compensation Plan liability		$	1,198	$	353	$	—	$	1,551
	Contingent acquisition consideration payable			—		—		75,294		75,294
	Total current liabilities			1,198		353		75,294		76,845
	Other long-term liabilities:
	Nonqualified Deferred Compensation Plan liability			25,402		5,884		—		31,286
	Forward foreign currency exchange contract (1)			—		805		—		805
	Contingent acquisition consideration payable			—		—		39,052		39,052
	Total other long-term liabilities			25,402		6,689		39,052		71,143
	Total liabilities		$	26,600	$	7,042	$	114,346	$	147,988
			Fair Value Measurements at December 31, 2014
			Quoted Price in		Significant Other		Significant		Total
			Active Markets		Observable		Unobservable
			For Identical		Inputs		Inputs
			Assets		(Level 2)		(Level 3)
			(Level 1)
	Assets:
	Cash and cash equivalents:
	Overnight deposits		$	225,159	$	—	$	—	$	225,159
	Money market instruments			—		650,327		—		650,327
	Total cash and cash equivalents			225,159		650,327		—		875,486
	Available-for-sale securities:
	Short-term:
	Certificates of deposit			—		54,174		—		54,174
	Corporate debt securities			—		15,532		—		15,532
	Long-term:
	Certificates of deposit			—		18,129		—		18,129
	Corporate debt securities			—		79,604		—		79,604
Greek government-issued bonds			—		123		—		123
Total available-for-sale securities			—		167,562		—		167,562
Other Current Assets:
Nonqualified Deferred Compensation Plan assets			—		514		—		514
Forward foreign currency exchange contract(1)			—		10,513		—		10,513
Restricted investments (2)			—		2,354		—		2,354
Embedded derivative (3)			—		—		2,386		2,386
Total other current assets			—		13,381		2,386		15,767
Other Assets:
Nonqualified Deferred Compensation Plan assets			—		5,112		—		5,112
Restricted investments (2)			—		5,387		—		5,387
Strategic investment (4)			30,811		—		—		30,811
Total other assets			30,811		10,499		—		41,310
Total assets		$	255,970	$	841,769	$	2,386	$	1,100,125
Liabilities:
Current Liabilities:
Nonqualified Deferred Compensation Plan liability		$	1,790	$	514	$	—	$	2,304
Forward foreign currency exchange contract(1)			—		12		—		12
Contingent acquisition consideration payable			—		—		3,895		3,895
Total current liabilities			1,790		526		3,895		6,211
Other long-term liabilities:
Nonqualified Deferred Compensation Plan liability			18,453		5,112		—		23,565
Contingent acquisition consideration payable			—		—		38,767		38,767
Total other long-term liabilities			18,453		5,112		38,767		62,332
Total liabilities		$	20,243	$	5,638	$	42,662	$	68,543
-1	See Note 14 to these Condensed Consolidated Financial Statements for further information regarding the derivative instruments.
-2	The restricted investments at March 31, 2015 and December 31, 2014 secure the Company’s irrevocable standby letter of credit obtained in connection with certain commercial agreements.
-3	The embedded derivative at December 31, 2014 represents the fair value of the conversion feature of a promissory note which may be settled in the issuer’s underlying shares.
-4	The Company has investments in marketable equity securities measured using quoted prices in an active market that are considered strategic investments. See Note 8 to these Condensed Consolidated Financial Statements for additional discussion regarding the Company’s strategic investments.
Liabilities Measured at Fair Value Using Level 3 Inputs
	Contingent acquisition consideration payable at December 31, 2014		$	42,662
	Addition of contingent consideration payable related to			71,402
	the Prosensa acquisition (CVR)
	Changes in the fair value of the contingent acquisition			282
	consideration payable
	Contingent acquisition consideration payable at March 31, 2015		$	114,346
Asset Retirement Obligation Liability and Corresponding Capital Asset
	Asset retirement obligations at December 31, 2014		$	3,765
	Accretion expense			36
	Additions			84
	Asset retirement obligations at March 31, 2015		$	3,885

STOCKBASED_COMPENSATION_Tables

STOCK-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option Valuation Assumptions	The assumptions used to estimate the per share fair value of stock options granted under the 2012 Inducement Plan and 2014 Inducement Plan and the Share Incentive Plan were as follows:
		Three Months Ended March 31,
		2015		2014
	Expected volatility	44 – 45%		44 – 45%
	Dividend yield		0.00%		0.00%
	Expected life	7.0 years		6.9 years
	Risk-free interest rate	1.5 – 2.0%		2.1 – 2.3%
Stock-Based Compensation Expense	Compensation expense included in the Company’s Condensed Consolidated Statements of Comprehensive Loss for all stock-based compensation arrangements was as follows:
		Three Months Ended March 31,
		2015		2014
	Cost of sales	$	1,348	$	1,086
	R&D		9,930		7,115
	SG&A		11,414		8,103
	Total stock-based compensation expense	$	22,692	$	16,304

COMPREHENSIVE_LOSS_Tables

COMPREHENSIVE LOSS (Tables)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Amounts Reclassified out of Accumulated Other Comprehensive Loss	The following table summarizes amounts reclassified out of Accumulated Other Comprehensive Income/(Loss) (AOCI) and their effect on the Company’s Condensed Consolidated Statements of Comprehensive Loss for the three months ended March 31, 2015 and 2014.
		Amount Reclassified from
		AOCI Gain (Loss)
		Three Months Ended March 31,						Consolidated Statement of
	Details about AOCI Components	2015			2014			Operations Classification
	Gains (loss) on cash flow hedges:
	Forward foreign currency exchange contracts	$	4,739		$	(887	)	Net product revenues
			—			320		Provision for income taxes
		$	4,739		$	(567	)	Net loss
Summary of Changes in Accumulated Balances of Other Comprehensive Income Loss Including Current Period Other Comprehensive Income and Reclassifications	The following table summarizes changes in the accumulated balances for each component of AOCI, including current period other comprehensive income and reclassifications out of AOCI, for the three months ended March 31, 2015 and 2014.
		Three Months Ended March 31, 2015
		Before Tax			Tax (Expense)			Net-of-Tax
		Amount			Benefit			Amount
	AOCI balance at December 31, 2014	$	33,984		$	(6,518	)	$	27,466
	Foreign currency translation adjustment		(5	)		—			(5	)
	Unrealized gain on available-for-sale securities:
	Unrealized holding gains		11,481			(4,160	)		7,321
	Less: reclassification adjustment for gain realized in net		—			—			—
	loss
	Net unrealized holding gain		11,481			(4,160	)		7,321
	Net unrealized holding gain on cash flow hedges:
	Unrealized holding gain		13,776			—			13,776
	Less: reclassification adjustment for gain realized in net		4,739			—			4,739
	loss
	Net unrealized holding gain		9,037			—			9,037
	Other comprehensive income		20,513			(4,160	)		16,353
	AOCI balance at March 31, 2015	$	54,497		$	(10,678	)	$	43,819
		Three Months Ended March 31, 2014
		Before Tax			Tax (Expense)			Net-of-Tax
		Amount			Benefit			Amount
	AOCI balance at December 31, 2013	$	7,756		$	(2,738	)	$	5,018
	Foreign currency translation adjustment		5			—			5
	Unrealized gain on available-for-sale securities:
	Unrealized holding gains		2,244			(821	)		1,423
	Less: reclassification adjustment for gain realized in net		—			—			—
	loss
	Net unrealized holding gain		2,244			(821	)		1,423
	Net unrealized holding gain on cash flow hedges:
	Unrealized holding gain		2,183			(787	)		1,396
	Less: reclassification adjustment for loss realized in net		(887	)		320			(567	)
	loss
	Net unrealized holding gain		1,296			(467	)		829
	Other comprehensive income		3,545			(1,288	)		2,257
	AOCI balance at March 31, 2014	$	11,301		$	(4,026	)	$	7,275

REVENUE_AND_CREDIT_CONCENTRATI1

REVENUE AND CREDIT CONCENTRATIONS (Tables) (Net Product Revenue)	3 Months Ended
	Mar. 31, 2015
Geographic Concentration Risk
Concentration Risk [Line Items]
Schedules of Consolidated Net Product Revenue Concentration	The table below summarizes consolidated net product revenue concentrations based on patient location for Vimizim, Naglazyme, Kuvan and Firdapse and the headquarters for Genzyme Corporation (Genzyme) for Aldurazyme. Although Genzyme sells Aldurazyme worldwide, the royalties earned by the Company on Genzyme’s net sales are included in the U.S. region, as the transactions are with Genzyme whose headquarters are located in the U.S.
			Three Months Ended March 31,
			2015			2014
	Region:
	United States			44	%		47	%
	Europe			21	%		20	%
	Latin America			17	%		16	%
	Rest of world			18	%		17	%
	Total net product revenue			100	%		100	%
Customer Concentration Risk
Concentration Risk [Line Items]
Schedules of Consolidated Net Product Revenue Concentration	The following table illustrates the percentage of the Company’s consolidated net product revenue attributed to the Company’s four largest customers.
			Three Months Ended March 31,
			2015			2014
	Customer A			15	%		16	%
	Customer B (1)			9	%		12	%
	Customer C			11	%		11	%
	Customer D			12	%		11	%
	Total			47	%		50	%
	-1	Genzyme is the Company’s sole customer for Aldurazyme and is responsible for marketing and selling Aldurazyme to third-parties. Net product revenues from Genzyme are comprised of royalties on worldwide net Aldurazyme sales and incremental product transfer revenue.

SEGMENT_INFORMATION_Tables

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information by Product Revenue	The Company operates in one business segment, which primarily focuses on the development and commercialization of innovative biopharmaceuticals for serious diseases and medical conditions. All products are included in one segment because the majority of our products have similar economic and other characteristics, including the nature of the products and production processes, type of customers, distribution methods and regulatory environment.
		Three Months Ended March 31,
		2015		2014
	Net product revenue by product:
	Vimizim	$	50,622	$	875
	Naglazyme		78,167		80,114
	Kuvan		50,193		45,236
	Aldurazyme		18,243		18,070
	Firdapse		4,087		4,709
	Total net product revenue	$	201,312	$	149,004
Summary of Total Revenues from External Customers and Collaborative Partners by Geographic Region	The following table summarizes total revenues from external customers and collaborative partners by geographic region.
		Three Months Ended March 31,
		2015		2014
	Total revenues by geographic region:
	United States	$	90,592	$	71,649
	Europe		41,710		30,654
	Latin America		34,818		22,209
	Rest of world		36,144		27,040
	Total revenues	$	203,264	$	151,552

Recovered_Sheet1

Nature of Operations and Business Risks - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
	Product
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of approved products	5
Accumulated deficit	($917,271)	($849,770)	[1]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Acquisitions_Additional_Inform

Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jan. 29, 2015	Mar. 10, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Business acquisitions, net of cash acquired	$538,392,000
Contractual right, share price			$4.14
Contractual right, amount			160,000,000
Fair value of intangible assets	114,300,000
Intangible assets			772,808,000
Net gain recognized due to early termination of lease and realization of remaining balance in deferred rent and reversal of asset retirement obligation		8,858,000
Prosensa’s other primary product candidates
Business Acquisition [Line Items]
Intangible assets			731,800,000
PRO 044
Business Acquisition [Line Items]
Intangible assets			16,900,000
PRO-045
Business Acquisition [Line Items]
Intangible assets			24,100,000
Vested Options
Business Acquisition [Line Items]
Business acquisition, cash paid			20,800,000
Prosensa Holding N.V
Business Acquisition [Line Items]
Business acquisitions, net of cash acquired			751,500,000
Business combination transaction costs	7,000,000		9,700,000		2,700,000
Business acquisition, cash paid			680,100,000
Prosensa Holding N.V | CVRs
Business Acquisition [Line Items]
Fair value of intangible assets			71,400,000
Prosensa Holding N.V | IPR&D
Business Acquisition [Line Items]
Fair value of intangible assets			772,800,000
Prosensa Holding N.V | Prosensa Shares
Business Acquisition [Line Items]
Business acquisition, cash paid			620,700,000
Approximate percentage of shares tendered at closing of initial offering			96.80%
Prosensa Holding N.V | Prosensa Shareholders
Business Acquisition [Line Items]
Business acquisition, cash paid			38,600,000
San Rafael Corporate Center
Business Acquisition [Line Items]
Business acquisition, cash paid				116,500,000
Net gain recognized due to early termination of lease and realization of remaining balance in deferred rent and reversal of asset retirement obligation		8,800,000
San Rafael Corporate Center | Royalty, License and Other Revenues
Business Acquisition [Line Items]
Tenant revenue, other real estate	1,000,000	400,000
San Rafael Corporate Center | Selling, General and Administrative
Business Acquisition [Line Items]
Business combination transaction costs		200,000
Net gain recognized due to early termination of lease and realization of remaining balance in deferred rent and reversal of asset retirement obligation		2,700,000
San Rafael Corporate Center | Research and Development
Business Acquisition [Line Items]
Net gain recognized due to early termination of lease and realization of remaining balance in deferred rent and reversal of asset retirement obligation		$6,100,000

Allocation_of_Purchase_Conside

Allocation of Purchase Consideration Including Contingent Acquisition Consideration Payable (Detail) (USD $)	Mar. 31, 2015	Jan. 29, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Business Combinations [Abstract]
Cash and cash equivalents		$141,669
Trade accounts receivable		3,086
Other current assets		1,537
Property, plant and equipment		2,683
Intangible assets		497
Other assets		104
Acquired IPR&D		772,808
Total identifiable assets acquired		922,384
Accounts payable and accrued expenses		-68,799
Debt assumed		-57,053
Deferred tax liability		-193,202
Total liabilities assumed		-319,054
Net identifiable assets acquired		603,330
Goodwill	202,392	148,134	54,258	[1]
Net assets acquired		$751,464
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Summary_of_Estimated_Fair_Valu

Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed (Detail) (USD $)	3 Months Ended	0 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 10, 2014	Jan. 29, 2015
Business Acquisition [Line Items]
Land improvements			$104
Intangible assets			497
Net identifiable assets acquired			603,330
San Rafael Corporate Center
Business Acquisition [Line Items]
Building and improvements		94,414
Land		14,565
Land improvements		3,616
Intangible assets		3,905
Net identifiable assets acquired		116,500
Estimated useful lives	Remaining lease terms
San Rafael Corporate Center | Building and Improvements
Business Acquisition [Line Items]
Estimated useful lives		50 years
San Rafael Corporate Center | Land Improvements
Business Acquisition [Line Items]
Estimated useful lives		10 years

Fair_Value_of_Identifiable_Int

Fair Value of Identifiable Intangible assets Acquired by Asset Class (Detail) (USD $)	Jan. 29, 2015	Mar. 10, 2014
In Thousands, unless otherwise specified
Business Acquisition [Line Items]
Fair value of identifiable intangible assets	$497
San Rafael Corporate Center
Business Acquisition [Line Items]
Fair value of identifiable intangible assets		3,905
San Rafael Corporate Center | Above Market Leases
Business Acquisition [Line Items]
Fair value of identifiable intangible assets		351
San Rafael Corporate Center | In Place Leases
Business Acquisition [Line Items]
Fair value of identifiable intangible assets		$3,554

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Jan. 31, 2015	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Equity [Abstract]
Common stock, shares issued	9,775,000	160,282,313		149,093,647	[1]
Common stock, issue price	$93.25
Proceeds from public offering of common stock, net	$888,300	$888,257	$117,464
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Computation_of_Basic_and_Dilut

Computation of Basic and Diluted Earnings per Common Share (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Net loss, basic	($67,501)	($38,115)
Gain on Company common stock issued to the NQDC		-374
Net loss, diluted	($67,501)	($38,489)
Weighted-average common shares outstanding, basic	157,612	143,983
Common stock issued to the NQDC		174
Weighted-average common shares outstanding, diluted	157,612	144,157
Net loss per common share, basic	($0.43)	($0.26)
Net loss per common share, diluted	($0.43)	($0.27)

AntiDilutive_Common_Stock_Excl

Anti-Dilutive Common Stock Excluded From Computation of Diluted Net Loss Per Share (Detail)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares of common stock excluded from computation of earnings (loss) per share as they are anti-dilutive	22,635	24,992
Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares of common stock excluded from computation of earnings (loss) per share as they are anti-dilutive	11,109	12,444
Common stock issuable under the 2017 Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares of common stock excluded from computation of earnings (loss) per share as they are anti-dilutive	1,567	3,047
Common stock issuable under the 2018 and 2020 Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares of common stock excluded from computation of earnings (loss) per share as they are anti-dilutive	7,966	7,966
Unvested restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares of common stock excluded from computation of earnings (loss) per share as they are anti-dilutive	1,557	1,326
Potentially issuable common stock for ESPP purchases
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares of common stock excluded from computation of earnings (loss) per share as they are anti-dilutive	223	209
Common stock held by the NQDC
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares of common stock excluded from computation of earnings (loss) per share as they are anti-dilutive	213

Net_Loss_Per_Common_Share_Addi

Net Loss Per Common Share - Additional Information (Detail) (USD $)	Mar. 31, 2015
Earnings Per Share [Line Items]
Debt instrument, convertible, conversion price, per share	$94.15
Convertible Notes due 2018
Earnings Per Share [Line Items]
Debt instrument, interest rate, stated percentage, per annum	0.75%
Convertible Notes due 2020
Earnings Per Share [Line Items]
Debt instrument, interest rate, stated percentage, per annum	1.50%

Amortized_Cost_Gross_Unrealize

Amortized Cost Gross Unrealized Holding Gain or Loss and Fair Value of Available for Sale Security by Major Security Type (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$331,824	$167,830
Gross Unrealized Holding Gains	215	74
Gross Unrealized Holding Losses		-342
Aggregate Fair Value	332,039	167,562
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	69,871	72,302
Gross Unrealized Holding Gains	1	1
Aggregate Fair Value	69,872	72,303
Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	147,537	95,478
Gross Unrealized Holding Gains	129
Gross Unrealized Holding Losses		-342
Aggregate Fair Value	147,666	95,136
Commercial Paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,354
Aggregate Fair Value	21,354
US Government Agencies Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	93,012
Gross Unrealized Holding Gains	31
Aggregate Fair Value	93,043
Greek Government-Issued Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	50	50
Gross Unrealized Holding Gains	54	73
Aggregate Fair Value	$104	$123

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
	Investment
Investments Debt And Equity Securities [Abstract]
Number of investments in marketable equity securities	2
Fair value of marketable equity securities	$41.80	$30.80
Carrying cost of non-marketable securities	3.1
Marketable equity securities, unrealized gain (loss)	$29.30	$18.30

Fair_Values_of_AvailableForSal

Fair Values of Available-For-Sale Securities by Contractual Maturity (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Investments Debt And Equity Securities [Abstract]
Maturing in one year or less	$108,119	$69,706
Maturing after one year through five years	223,920	97,856
Total	$332,039	$167,562

Recovered_Sheet2

Goodwill - Schedule of Changes in Goodwill (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Jan. 29, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Beginning Balance	$54,258	[1]	$148,134
Addition of goodwill related to the acquisition of Prosensa	148,134
Ending Balance	$202,392		$148,134
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Intangible_Assets_Detail

Intangible Assets (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Intangible assets:
Finite-lived intangible assets	$123,836	$123,365
Indefinite-lived intangible assets	847,238	74,430
Gross intangible assets:	971,074	197,795
Less: Accumulated amortization	-44,178	-41,217
Net carrying value	$926,896	$156,578	[1]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Property_Plant_and_Equipment_D

Property Plant and Equipment (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$778,429	$752,405
Less: Accumulated depreciation	-240,312	-228,889
Total property, plant and equipment, net	538,117	523,516	[1]
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	40,733	39,297
Building and Improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	339,161	335,991
Manufacturing and Laboratory Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	129,348	124,564
Computer Hardware and Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	99,879	97,032
Furniture and Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,874	13,717
Land Improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,106	4,106
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	29,357	29,358
Construction-in-Progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$120,971	$108,340
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Property_Plant_and_Equipment_A

Property Plant and Equipment - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Property Plant And Equipment [Abstract]
Depreciation expense	$11,500,000	$9,600,000
Depreciation expense capitalized into inventory	$3,580,000	$2,924,000

Schedule_of_Inventory_Detail

Schedule of Inventory (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]
Raw materials	$21,690	$22,488
Work-in-process	124,192	114,393
Finished goods	76,951	62,571
Total inventory	$222,833	$199,452	[1]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Schedule_of_Other_Current_Asse

Schedule of Other Current Assets (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Condensed Financial Information Of Subsidiaries Disclosure [Abstract]
Prepaid expenses	$39,159	$35,390
Short-term forward currency exchange contract assets	18,337	10,513
Promissory notes receivable, net	3,326	46,946
Restricted investments	7,131	2,354
Convertible promissory note conversion option		2,386
Other receivables	10,983	9,733
Other	5,329	4,513
Total other current assets	$84,265	$111,835	[1]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Schedule_of_Other_Assets_Detai

Schedule of Other Assets (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Condensed Financial Information Of Subsidiaries Disclosure [Abstract]
Deposits	$11,045	$12,021
Deferred debt offering costs	10,911	11,763
Strategic investments	44,918	30,811
Long-term forward foreign currency exchange contract assets	7,391	5,387
Other	6,067	5,299
Total other assets	$80,332	$65,281	[1]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Schedule_of_Accounts_Payable_a

Schedule of Accounts Payable and Accrued Liabilities (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Accounts payable	$23,606	$32,779
Accrued accounts payable	106,462	98,490
Accrued compensation expense	32,461	45,479
Accrued vacation expense	15,871	12,540
Accrued rebates payable	17,173	14,859
Accrued royalties payable	7,207	9,050
Value added taxes payable	5,730	5,479
Other accrued operating expenses	8,721	8,244
Other	12,981	4,924
Total accounts payable and accrued liabilities	$230,212	$231,844	[1]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Summary_of_Convertible_Debt_De

Summary of Convertible Debt (Detail) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Debt Instrument [Line Items]
Long-term Convertible Notes, net of unamortized discount	$655,491		$657,976	[1]
Convertible Notes, fair value	1,319,808		1,079,792
Convertible Notes due 2020
Debt Instrument [Line Items]
Long-term Convertible Notes, net of unamortized discount	300,786		297,955
Convertible Notes, fair value	568,444	[2]	456,360	[2]
Convertible Notes due 2018
Debt Instrument [Line Items]
Long-term Convertible Notes, net of unamortized discount	322,807		319,463
Convertible Notes, fair value	555,994	[2]	442,448	[2]
Convertible Notes due 2017
Debt Instrument [Line Items]
Long-term Convertible Notes, net of unamortized discount	31,898		40,558
Convertible Notes, fair value	$195,370	[2]	$180,984	[2]
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.
[2]	The fair value of the Company’s fixed rate convertible debt is based on open market trades and is classified as Level 1 in the fair value hierarchy.

Summary_of_Convertible_Debt_Pa

Summary of Convertible Debt (Parenthetical) (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Convertible Notes due 2020
Debt Instrument [Line Items]
Long-term convertible debt, unamortized discount	$74,214	$77,045
Convertible Notes due 2018
Debt Instrument [Line Items]
Long-term convertible debt, unamortized discount	$52,193	$55,537

Summary_of_Interest_Expense_on

Summary of Interest Expense on Convertible Debt (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Schedule Of Interest Expenses [Line Items]
Total interest expense on convertible debt	$9,462	$9,106
Convertible Senior Notes
Schedule Of Interest Expenses [Line Items]
Coupon interest	2,462	2,408
Amortization of issuance costs	826	843
Accretion of debt discount	6,174	5,855
Total interest expense on convertible debt	$9,462	$9,106

Convertible_Debt_Additional_In

Convertible Debt - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015
Debt Conversion [Line Items]
Convertible cash premium paid to holder for agreeing to convert	$163,000
Convertible Notes due 2017
Debt Conversion [Line Items]
Number of agreements	3
Convertible Notes due 2017 | Agreement One
Debt Conversion [Line Items]
Convertible notes aggregate principal	8,100,000
Notes converted, number of shares	399,469
Convertible cash premium paid to holder for agreeing to convert	200,000
Convertible Notes due 2017 | Agreement One | Convertible Senior Notes
Debt Conversion [Line Items]
Convertible cash premium paid to holder for agreeing to convert	$200,000

Recovered_Sheet3

Derivative Instruments and Hedging Strategies - Additional Information (Detail)

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

Mar. 31, 2015

Mar. 31, 2014

Dec. 31, 2014

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

Mar. 31, 2015

USD ($)

USD ($)

USD ($)

Minimum

Maximum

Foreign Currency Derivatives

Foreign Currency Derivatives

Derivatives Designated As Hedging Instruments

Derivatives Designated As Hedging Instruments

Derivatives Designated As Hedging Instruments

Derivatives Designated As Hedging Instruments

Not Designated as Hedging Instrument

Not Designated as Hedging Instrument

Not Designated as Hedging Instrument

Not Designated as Hedging Instrument

USD ($)

Maximum

Euro

Purchase

Foreign Currency Derivatives

Foreign Currency Derivatives

Derivative

Sale Contracts

Foreign Currency Derivatives

Foreign Currency Derivatives

Derivative

Euro

Sale Contracts

Purchase

Derivative

Sale Contracts

Sale Contracts

Derivative

EUR (€)

Sale Contracts

EUR (€)

GBP (£)

EUR (€)

Derivative [Line Items]

Number of forward foreign currency exchange contracts outstanding

94

7

1

1

Outstanding forward foreign currency exchange contracts

€ 131,600,000

€ 20,000,000

€ 42,100,000

£ 6,400,000

Maturity period of foreign currency derivatives

1-Apr-15

31-Mar-18

31-Mar-18

30-Apr-15

Amount reclassified from accumulated other comprehensive income to earnings as related to forecasted revenue transactions

4,739,000

567,000

18,900,000

Maximum length of time over which hedging its exposure to the reduction in value of forecasted foreign currency cash flows through foreign currency forward contracts

12 months

Gain (Loss) from foreign currency exchange contracts in accumulated other comprehensive income

$24,500,000

$15,900,000

Recovered_Sheet4

Derivative Instruments and Hedging Strategies (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Derivative [Line Items]
Derivative Asset, Fair Value	$25,728	$15,900
Derivative Liability, Fair Value	805	12
Derivatives Designated As Hedging Instruments
Derivative [Line Items]
Derivative Asset, Fair Value	25,562	15,593
Derivatives Designated As Hedging Instruments | Forward Foreign Currency Exchange Contracts | Other Current Assets
Derivative [Line Items]
Derivative Asset, Fair Value	18,171	10,206
Derivatives Designated As Hedging Instruments | Forward Foreign Currency Exchange Contracts | Other Assets
Derivative [Line Items]
Derivative Asset, Fair Value	7,391	5,387
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value	166	307
Derivative Liability, Fair Value	805	12
Not Designated as Hedging Instrument | Forward Foreign Currency Exchange Contracts | Other Current Assets
Derivative [Line Items]
Derivative Asset, Fair Value	166
Not Designated as Hedging Instrument | Forward Foreign Currency Exchange Contracts | Other Assets
Derivative [Line Items]
Derivative Asset, Fair Value		307
Not Designated as Hedging Instrument | Forward Foreign Currency Exchange Contracts | Accounts Payable and Accrued Liabilities
Derivative [Line Items]
Derivative Liability, Fair Value		12
Not Designated as Hedging Instrument | Forward Foreign Currency Exchange Contracts | Other Long-Term Liabilities
Derivative [Line Items]
Derivative Liability, Fair Value	$805

Effect_of_Derivative_Instrumen

Effect of Derivative Instruments (Detail) (USD $)	3 Months Ended		12 Months Ended	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014	Mar. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Net gain recognized in Other Comprehensive Income (OCI)	$24,500		$15,900
Forward Foreign Currency Exchange Contracts | Derivatives Designated As Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net gain recognized in Other Comprehensive Income (OCI)	13,776	[1]		1,396	[1]
Net gain reclassified from accumulated OCI into income	4,739	[2]		-567	[2]
Net gain (loss) recognized in net loss	141	[3]		-121	[3]
Forward Foreign Currency Exchange Contracts | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) recognized in net loss	$7,800	[4]		$56	[4]
[1]	Net change in the fair value of the effective portion classified as OCI.
[2]	Effective portion classified as net product revenue.
[3]	Ineffective portion and amount excluded from effectiveness testing classified as SG&A expense.
[4]	Classified as SG&A expense.

Fair_Value_of_Financial_Assets

Fair Value of Financial Assets and Liabilities (Detail) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities	$332,039		$167,562
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents	900,570		875,486
Fair value of Available-for-sale securities	332,039		167,562
Fair value of other current assets	25,821		15,767
Fair value of other non-current assets	55,084		41,310
Fair value of financial assets, Total	1,313,514		1,100,125
Fair value of other current liabilities	76,845		6,211
Fair value of other non-current liabilities	71,143		62,332
Fair value of financial liabilities, Total	147,988		68,543
Fair Value, Measurements, Recurring | Overnight Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents	833,545		225,159
Fair Value, Measurements, Recurring | Money Market Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents	67,025		650,327
Fair Value, Measurements, Recurring | Nonqualified Deferred Compensation Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	1,551		2,304
Fair value of other non-current liabilities	31,286		23,565
Fair Value, Measurements, Recurring | Contingent Acquisition Consideration Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	75,294		3,895
Fair value of other non-current liabilities	39,052		38,767
Fair Value, Measurements, Recurring | Forward Foreign Currency Exchange Contract, Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities			12	[1]
Fair value of other non-current liabilities	805	[1]
Fair Value, Measurements, Recurring | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current	57,176		54,174
Fair value of Available-for-sale securities, non-current	12,696		18,129
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current	15,546		15,532
Fair value of Available-for-sale securities, non-current	132,120		79,604
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current	21,354
Fair Value, Measurements, Recurring | US Government Agencies Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current	14,043
Fair value of Available-for-sale securities, non-current	79,000
Fair Value, Measurements, Recurring | Greek Government-Issued Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, non-current	104		123
Fair Value, Measurements, Recurring | Nonqualified Deferred Compensation Plan Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	353		514
Fair value of other non-current assets	5,884		5,112
Fair Value, Measurements, Recurring | Forward Foreign Current Exchange Contract Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	18,337	[1]	10,513	[1]
Fair value of other non-current assets	7,391	[1]
Fair Value, Measurements, Recurring | Restrictive Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	7,131	[2]	2,354	[2]
Fair value of other non-current assets			5,387	[2]
Fair Value, Measurements, Recurring | Strategic Investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	41,809	[3]	30,811	[3]
Fair Value, Measurements, Recurring | Embedded Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets			2,386	[4]
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 Cash and cash equivalents	833,545		225,159
Fair value of other non-current assets	41,809		30,811
Fair value of financial assets, Total	875,354		255,970
Fair value of other current liabilities	1,198		1,790
Fair value of other non-current liabilities	25,402		18,453
Fair value of financial liabilities, Total	26,600		20,243
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Overnight Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents	833,545		225,159
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Nonqualified Deferred Compensation Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	1,198		1,790
Fair value of other non-current liabilities	25,402		18,453
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Strategic Investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	41,809	[3]	30,811	[3]
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 Cash and cash equivalents	67,025		650,327
Fair value of Available-for-sale securities	332,039		167,562
Fair value of other current assets	25,821		13,381
Fair value of other non-current assets	13,275		10,499
Fair value of financial assets, Total	438,160		841,769
Fair value of other current liabilities	353		526
Fair value of other non-current liabilities	6,689		5,112
Fair value of financial liabilities, Total	7,042		5,638
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Money Market Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents	67,025		650,327
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Nonqualified Deferred Compensation Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	353		514
Fair value of other non-current liabilities	5,884		5,112
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Forward Foreign Currency Exchange Contract, Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities			12	[1]
Fair value of other non-current liabilities	805	[1]
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current	57,176		54,174
Fair value of Available-for-sale securities, non-current	12,696		18,129
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current	15,546		15,532
Fair value of Available-for-sale securities, non-current	132,120		79,604
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current	21,354
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | US Government Agencies Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current	14,043
Fair value of Available-for-sale securities, non-current	79,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Greek Government-Issued Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, non-current	104		123
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Nonqualified Deferred Compensation Plan Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	353		514
Fair value of other non-current assets	5,884		5,112
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Forward Foreign Current Exchange Contract Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	18,337	[1]	10,513	[1]
Fair value of other non-current assets	7,391	[1]
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Restrictive Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	7,131	[2]	2,354	[2]
Fair value of other non-current assets			5,387	[2]
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			2,386
Fair value of financial assets, Total			2,386
Fair value of other current liabilities	75,294		3,895
Fair value of other non-current liabilities	39,052		38,767
Fair value of financial liabilities, Total	114,346		42,662
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Contingent Acquisition Consideration Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	75,294		3,895
Fair value of other non-current liabilities	39,052		38,767
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Embedded Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets			$2,386	[4]
[1]	See Note 14 to these Condensed Consolidated Financial Statements for further information regarding the derivative instruments.
[2]	The restricted investments at March 31, 2015 and December 31, 2014 secure the Company’s irrevocable standby letter of credit obtained in connection with certain commercial agreements.
[3]	The Company has investments in marketable equity securities measured using quoted prices in an active market that are considered strategic investments. See Note 8 to these Condensed Consolidated Financial Statements for additional discussion regarding the Company’s strategic investments.
[4]	The embedded derivative at December 31, 2014 represents the fair value of the conversion feature of a promissory note which may be settled in the issuer’s underlying shares.

Liabilities_Measured_at_Fair_V

Liabilities Measured at Fair Value Using Level 3 Inputs (Detail) (Contingent Payment, USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Contingent Payment
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent acquisition consideration payable, Beginning balance	$42,662
Addition of contingent consideration payable related to the Prosensa acquisition (CVR)	71,402
Changes in the fair value of the contingent acquisition consideration payable	282
Contingent acquisition consideration payable, Ending balance	$114,346

Asset_Retirement_Obligation_Li

Asset Retirement Obligation Liability and Corresponding Capital Asset (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset retirement obligation, Beginning balance	$3,765
Accretion expense	36
Additions	84
Asset retirement obligations, Ending balance	$3,885

Assumptions_Used_to_Estimate_P

Assumptions Used to Estimate Per Share Fair Value of Stock Options Granted (Detail) (Stock Option)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%
Expected life	7 years	6 years 10 months 24 days
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	44.00%	44.00%
Risk-free interest rate	1.50%	2.10%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	45.00%	45.00%
Risk-free interest rate	2.00%	2.30%

Stock_Based_Compensation_Addit

Stock Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 03, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, granted	642,070
Weighted-average fair value per option granted	$56.11
Recognized compensation costs	$22,692,000	$16,304,000
Stock-based compensation capitalized to inventory	2,500,000	2,100,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, granted	825,900
Weighted-average fair value per option granted	$120.95
Restricted Stock With Performance and Market Based Vesting Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value per option granted	$34.66
Number of restricted stock units grants	860,000
Recognized compensation costs	1,800,000	600,000
Restricted Stock With Performance and Market Based Vesting Conditions | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shareholder return, percentage of multiplier range	75.00%
Restricted Stock With Performance and Market Based Vesting Conditions | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shareholder return, percentage of multiplier range	125.00%
Restricted Stock Unit Awards with Performance Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value per option granted	$108.36
Number of restricted stock units grants			58,300
Recognized compensation costs	$200,000
Award vesting service period			3 years
Number of units that could vest if performance condition is achieved and a revenue multiplier is applied			69,960
Restricted Stock Unit Awards with Performance Conditions | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Revenue multiplier			0.8
Restricted Stock Unit Awards with Performance Conditions | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Revenue multiplier			1.2

Compensation_Expense_Detail

Compensation Expense (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$22,692	$16,304
Cost of Sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1,348	1,086
R&D
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	9,930	7,115
SG&A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$11,414	$8,103

Amounts_Reclassified_out_of_Ac

Amounts Reclassified out of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net product revenues	$201,312	$149,004
Provision for (benefit from) income taxes	7,202	-3,491
NET LOSS	-67,501	-38,115
Amount Reclassified from AOCI Gain (Loss) | Gain (loss) on cash flow hedges: | Forward Foreign Currency Exchange Contracts
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net product revenues	4,739	-887
Provision for (benefit from) income taxes		320
NET LOSS	$4,739	($567)

Summary_of_Changes_in_Accumula

Summary of Changes in Accumulated Balances of Other Comprehensive Income Loss Including Current Period Other Comprehensive Income and Reclassifications (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Equity [Abstract]
Beginning Balance, before tax amount	$33,984		$7,756
Foreign currency translation adjustment, before tax amount	-5		5
Unrealized gain on available-for-sale securities, before tax amount
Unrealized holding gains, before tax amount	11,481		2,244
Net unrealized holding gain, before tax amount	11,481		2,244
Net unrealized holding gain (loss) on cash flow hedges, before tax amount
Unrealized holding gain (loss), before tax amount	13,776		2,183
Less: reclassification adjustment for gain (loss) realized in net income (loss), before tax amount	4,739		-887
Net unrealized holding gain (loss), before tax amount	9,037		1,296
Other comprehensive income, before tax amount	20,513		3,545
Ending Balance, before tax amount	54,497		11,301
Beginning Balance, tax (expense) benefit	-6,518		-2,738
Unrealized gain on available-for-sale securities, tax (expense) benefit
Unrealized holding gains, tax (expense) benefit	-4,160		-821
Net unrealized holding gain, tax (expense) benefit	-4,160		-821
Net unrealized holding gain (loss) on cash flow hedges, tax (expense) benefit
Unrealized holding gain (loss), tax (expense) benefit			-787
Less: reclassification adjustment for gain (loss) realized in net income (loss), tax (expense) benefit			320
Net unrealized holding gain (loss), tax (expense) benefit			-467
Other comprehensive income, tax (expense) benefit	-4,160		-1,288
Ending Balance, tax (expense) benefit	-10,678		-4,026
Beginning Balance, net of tax amount	27,466	[1]	5,018
Foreign currency translation adjustment, net of tax amount	-5		5
Unrealized gain on available-for-sale securities, net of tax amount
Unrealized holding gains, net of tax amount	7,321		1,423
Net unrealized holding gain, net of tax amount	7,321		1,423
Net unrealized holding gain (loss) on cash flow hedges, net of tax amount
Unrealized holding gain (loss), net of tax amount	13,776		1,396
Less: reclassification adjustment for gain (loss) realized in net income (loss), net of tax amount	4,739		567
Net unrealized holding gain (loss), net of tax amount	9,037		829
Other comprehensive income, net of tax amount	16,353		2,257
Ending Balance, net of tax amount	$43,819		$7,275
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Consolidated_Net_Product_Reven

Consolidated Net Product Revenue Concentrations Based on Patient Location (Detail) (Geographic Concentration Risk, Net Product Revenue)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Concentration Risk [Line Items]
Concentration risk, percentage	100.00%	100.00%
UNITED STATES
Concentration Risk [Line Items]
Concentration risk, percentage	44.00%	47.00%
Europe
Concentration Risk [Line Items]
Concentration risk, percentage	21.00%	20.00%
Latin America
Concentration Risk [Line Items]
Concentration risk, percentage	17.00%	16.00%
Rest of World
Concentration Risk [Line Items]
Concentration risk, percentage	18.00%	17.00%

Consolidated_Net_Product_Reven1

Consolidated Net Product Revenue Concentrations Attributed to Largest Customers (Detail) (Customer Concentration Risk, Net Product Revenue)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Concentration Risk [Line Items]
Concentration risk, percentage	47.00%		50.00%
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	15.00%		16.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage	9.00%	[1]	12.00%	[1]
Customer C
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%		11.00%
Customer D
Concentration Risk [Line Items]
Concentration risk, percentage	12.00%		11.00%
[1]	Genzyme is the Company’s sole customer for Aldurazyme and is responsible for marketing and selling Aldurazyme to third-parties. Net product revenues from Genzyme are comprised of royalties on worldwide net Aldurazyme sales and incremental product transfer revenue.

Recovered_Sheet5

Revenue and Credit Concentrations - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended		3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014		Mar. 31, 2014
	Customer	Customer
Concentration Risk [Line Items]
Accounts receivable, net	$175,738,000	$144,472,000	[1]
Southern European Countries
Concentration Risk [Line Items]
Total amount past due	12,000,000
Southern European Countries | Greater than 90 days
Concentration Risk [Line Items]
Total amount past due	800,000
Southern European Countries | Greater than 180 days
Concentration Risk [Line Items]
Total amount past due	400,000
Southern European Countries | Greater than 365 days
Concentration Risk [Line Items]
Total amount past due	100,000
Largest Customers
Concentration Risk [Line Items]
Number of customers accounted for largest balance in accounts receivable	2	2
Accounts receivable, net	$30,200,000	$34,500,000
Credit Concentration Risk | Accounts Receivable | Larger Customer One
Concentration Risk [Line Items]
Concentration risk, percentage	29.00%	42.00%
Credit Concentration Risk | Accounts Receivable | Larger Customer Two
Concentration Risk [Line Items]
Concentration risk, percentage	21.00%	18.00%
Geographic Concentration Risk | Accounts Receivable | Southern European Countries
Concentration Risk [Line Items]
Concentration risk, percentage	7.00%
Geographic Concentration Risk | Net Product Revenue
Concentration Risk [Line Items]
Concentration risk, percentage	100.00%			100.00%
Geographic Concentration Risk | Net Product Revenue | Southern European Countries
Concentration Risk [Line Items]
Concentration risk, percentage	4.00%
[1]	December 31, 2014 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, 2014, filed with the Securities and Exchange Commission (the SEC) on March 2, 2015.

Segment_Information_Additional

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015
	Segment
Segment Reporting [Abstract]
Number of operating business segment	1

Segment_Information_by_Product

Segment Information by Product Revenue (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenue from External Customer [Line Items]
Net product revenues	$201,312	$149,004
Vimizim
Revenue from External Customer [Line Items]
Net product revenues	50,622	875
Naglazyme
Revenue from External Customer [Line Items]
Net product revenues	78,167	80,114
Kuvan
Revenue from External Customer [Line Items]
Net product revenues	50,193	45,236
Aldurazyme
Revenue from External Customer [Line Items]
Net product revenues	18,243	18,070
Firdapse
Revenue from External Customer [Line Items]
Net product revenues	$4,087	$4,709

Summary_of_Total_Revenues_from

Summary of Total Revenues from External Customers and Collaborative Partners by Geographic Region (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenue from External Customer [Line Items]
Total revenues	$203,264	$151,552
UNITED STATES
Revenue from External Customer [Line Items]
Total revenues	90,592	71,649
Europe
Revenue from External Customer [Line Items]
Total revenues	41,710	30,654
Latin America
Revenue from External Customer [Line Items]
Total revenues	34,818	22,209
Rest of World
Revenue from External Customer [Line Items]
Total revenues	$36,144	$27,040

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain regulatory and licensing milestones	$733.40
Fair value of intangible assets	114.3
Purchase commitment for the next five years	74
Current Liabilities
Commitments And Contingencies [Line Items]
Fair value of intangible assets	75.3
Completed Programs
Commitments And Contingencies [Line Items]
Contingent payments upon achievement of certain regulatory and licensing milestones	$51.40