Credit Facilities - Narrative (Details)						1 Months Ended	12 Months Ended
	Aug. 09, 2018 USD ($) day shares	Jan. 12, 2018 USD ($)	Apr. 03, 2017 USD ($)	Jun. 02, 2016 USD ($)	Dec. 10, 2013 USD ($)	Feb. 29, 2016 USD ($)	Dec. 31, 2018 USD ($) day	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Nov. 20, 2018 USD ($)	Nov. 02, 2015 USD ($) $ / shares
Debt Instrument [Line Items]
Repayments of Convertible Debt							$ 18,278,000	$ 66,613,000	$ 0
Long-term Debt							198,078,000	225,476,000
Payable in kind interest expense on term loan facility							3,084,000	0	0
Derivative liabilities							4,012,000	0
Gain (loss) on derivative							12,097,000	0	(43,831,000)
Debt termination fees paid							1,310,000	2,515,000	0
Outstanding borrowings relating to revolving loan facility							0	21,000
Loss on debt extinguishment							2,270,000	6,512,000	$ 0
Note payable that was converted from a refund payable							4,281,000	0
Term loan
Debt Instrument [Line Items]
Long-term Debt							117,880,000	102,008,000
Term loan | Facility Agreement
Debt Instrument [Line Items]
Debt instrument, face amount			$ 120,000,000
Deferred financing costs, gross			5,100,000
Term loan | Amended Facility Agreement
Debt Instrument [Line Items]
Debt instrument, face amount	$ 160,500,000.0
Debt instrument, stated interest rate	5.00%
Additional indebtedness	$ 40,500,000
Long-term Debt	$ 113,100,000						117,900,000
Interest rate, payable in kind	4.75%
Maximum shares issuable to satisfy obligation to pay interest owed | shares	252,680
Percentage of market value attributable to interest that is paid with common stock	96.00%
Trailing number of days used to calculate weighted average price per share used to calculate interest value | day	10
Percentage of market value attributable to principal that is paid with common stock	96.00%
Trailing number of days used to calculate weighted average price per share used to calculate principal value | day	3
Maximum number of shares under mandatory redemption | shares	1,430,001
Principal amount of loan converted into stock to credit first against principal and payable in kind interest due 2021	$ 60,000,000
Termination fee payable	6,100,000
Debt discount	47,400,000
Deferred financing costs, net							4,200,000
Payable in kind interest expense on term loan facility							1,100,000
Convertible senior notes
Debt Instrument [Line Items]
Long-term Debt							75,917,000	123,447,000
Amount of conversion features that were re-classed from stockholders' equity to derivative liabilities						$ 24,800,000
Amount of conversion features that were re-classed from derivative liabilities to additional paid-in capital				$ 68,600,000
Convertible senior notes | Convertible Senior Notes Due 2020
Debt Instrument [Line Items]
Debt instrument, principal repurchased	$ 40,500,000.0
Debt instrument, stated interest rate	3.25%
Convertible senior notes | Convertible Senior Notes Issued November 2015
Debt Instrument [Line Items]
Debt instrument, face amount												$ 125,000,000
Deferred financing costs, gross												$ 3,700,000
Debt instrument, stated interest rate												3.25%
Deferred financing costs, net							$ 800,000
Convertible debt redemption, trading days threshold | day							20
Convertible debt redemption, consecutive trading days threshold | day							30
Convertible debt redemption, percentage of stock price trigger							130.00%
Redemption date minimum trading days							30 days
Trading days prior to redemption to elect to convert							2 days
Redemption price, percentage							100.00%
Face amount of each note that is convertible							$ 1,000
Convertible debt, conversion ratio							8.94314
Convertible debt, conversion price (usd per share) | $ / shares												$ 111.82
Initial fair value of the indebtedness										$ 97,800,000
Amount allocated to the embedded conversion option										$ 27,200,000
Outstanding borrowings related to the senior notes							$ 76,800,000
Convertible senior notes | Convertible Senior Notes Issued December 2013
Debt Instrument [Line Items]
Debt instrument, face amount					$ 86,300,000.0
Debt instrument, principal repurchased	$ 68,000,000
Debt instrument, stated interest rate					2.25%
Repayments of Convertible Debt							18,300,000
Proceeds from the sale of senior notes					$ 82,600,000
Reduction of embedded conversion option							2,200,000
Loss on debt extinguishment								(3,200,000)
Minimum | Term loan | Amended Facility Agreement
Debt Instrument [Line Items]
Estimated annual interest expense							4,100,000
Minimum | Convertible senior notes | Convertible Senior Notes Issued November 2015
Debt Instrument [Line Items]
Estimated annual interest expense							6,400,000
Maximum | Term loan | Amended Facility Agreement
Debt Instrument [Line Items]
Estimated annual interest expense							31,000,000
Maximum | Convertible senior notes | Convertible Senior Notes Issued November 2015
Debt Instrument [Line Items]
Estimated annual interest expense							7,200,000
2017 Deerfield Warrants
Debt Instrument [Line Items]
Deferred financing costs, gross			$ 400,000
Period until expiration of warrants			7 years
Percentage of common stock limiting exercise of warrants			4.985%
Fair value of warrants			$ 14,300,000
2018 Deerfield Warrants
Debt Instrument [Line Items]
Deferred financing costs, gross	$ 100,000
Period until expiration of warrants	7 years
Fair value of warrants	$ 10,300,000
Derivative liabilities | 2018 Deerfield Warrants
Debt Instrument [Line Items]
Derivative liabilities	16,400,000
Long-term debt | Convertible senior notes | Convertible Senior Notes Issued November 2015
Debt Instrument [Line Items]
Deferred financing costs, gross												$ 2,900,000
Additional Paid-In Capital | Convertible senior notes | Convertible Senior Notes Issued November 2015
Debt Instrument [Line Items]
Deferred financing costs, gross												$ 800,000
Japan Lifeline Co., Ltd.
Debt Instrument [Line Items]
Note payable that was converted from a refund payable											$ 4,300,000
Japan Lifeline Co., Ltd. | Other notes payable
Debt Instrument [Line Items]
Debt instrument, stated interest rate											2.50%
Revolving loan facility | Deerfield ELGX Revolver, LLC
Debt Instrument [Line Items]
Deferred financing costs, gross			1,200,000
Deferred financing costs, net							600,000
Revolving credit facility, maximum borrowing capacity	50,000,000		$ 50,000,000
Debt termination fees paid		$ 1,300,000
Write off of unamortized deferred financing		$ 1,000,000
Revolving loan facility, availability	$ 24,000,000						13,700,000
Variable rate floor	1.00%
Basis spread	5.50%
Minimum amount on which interest will accrue	$ 9,750,000
Total commitment fee	500,000
Global liquidity requirement	22,500,000.0
Outstanding borrowings relating to revolving loan facility							0
Loss on debt extinguishment							$ 2,300,000
Revolving loan facility | Deerfield ELGX Revolver, LLC | Other assets
Debt Instrument [Line Items]
Deferred financing costs, gross	600,000
Revolving loan facility | MidCap Financial Trust
Debt Instrument [Line Items]
Deferred financing costs, net								800,000
Debt termination fees paid								2,500,000
Loss on debt extinguishment								$ 3,300,000
Revolving loan facility | Closing | Deerfield ELGX Revolver, LLC
Debt Instrument [Line Items]
Commitment fee payable	200,000
Revolving loan facility | First Anniversary | Deerfield ELGX Revolver, LLC
Debt Instrument [Line Items]
Commitment fee payable	$ 200,000
Early termination or reduction fee percentage	2.50%
Revolving loan facility | Second Anniversary | Deerfield ELGX Revolver, LLC
Debt Instrument [Line Items]
Commitment fee payable	$ 100,000
Early termination or reduction fee percentage	1.50%
Revolving loan facility | Expiration | Deerfield ELGX Revolver, LLC
Debt Instrument [Line Items]
Exit fee payable	$ 1,000,000
Revolving loan facility | Third Anniversary | Deerfield ELGX Revolver, LLC
Debt Instrument [Line Items]
Early termination or reduction fee percentage	0.50%
Revolving loan facility | Thereafter | Deerfield ELGX Revolver, LLC
Debt Instrument [Line Items]
Early termination or reduction fee percentage	0.00%
Debt Instrument, Redemption, Period Two | Convertible senior notes | Convertible Senior Notes Issued November 2015
Debt Instrument [Line Items]
Convertible debt redemption, consecutive trading days threshold | day							5
Convertible debt redemption, percentage of stock price trigger							98.00%
Threshold business days							5 days