Credit Facilities (Details)								1 Months Ended	3 Months Ended			6 Months Ended
	Apr. 03, 2017 USD ($) $ / shares shares	Jul. 29, 2016 USD ($)	Jun. 02, 2016 USD ($) shares	Feb. 03, 2016 shares	Nov. 02, 2015 USD ($) $ / shares	Jul. 21, 2015 USD ($)	Dec. 10, 2013 USD ($) $ / shares $ / security	Feb. 29, 2016 USD ($)	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) d $ / shares shares	Jun. 30, 2016 USD ($)	Dec. 31, 2016 shares	Jun. 01, 2016 shares	Dec. 31, 2015 USD ($)	Nov. 30, 2015 USD ($)
Line of Credit Facility [Line Items]
Non-cash loss on debt extinguishment									$ 6,512,000		$ 0	$ 6,512,000	$ 0
Payments of derivative issuance costs							$ 7,400,000
Common stock authorized (in shares) | shares			135,000,000						135,000,000	135,000,000		135,000,000		135,000,000	100,000,000
Adjustments to additional paid-in capital, conversion features of Senior Notes			$ 68,600,000
Change in fair value of derivative liabilities									$ 0		$ (38,743,000)	$ 0	$ (43,831,000)
Revolving Credit Facility | Bank of America
Line of Credit Facility [Line Items]
Aggregate maximum borrowing capacity						$ 20,000,000
Minimum current ratio												1.5
Revolving Credit Facility | MidCap
Line of Credit Facility [Line Items]
Aggregate maximum borrowing capacity		$ 50,000,000.0
Deferred financing costs - professional fees									900,000	$ 900,000		$ 900,000
Restricted cash									2,000,000	2,000,000		2,000,000
Write off of deferred financing costs										800,000
Debt termination fees										2,500,000
Revolving Credit Facility | MidCap | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate		4.10%
Variable rate, maximum		0.50%
Revolving Credit Facility | Deerfield Revolver
Line of Credit Facility [Line Items]
Deferred finance costs, noncurrent, net									1,100,000	1,100,000		1,100,000
Debt issuance costs	$ 1,200,000
Aggregate maximum borrowing capacity	$ 50,000,000
Restricted cash									2,000,000	2,000,000		2,000,000
Amount outstanding									24,300,000	24,300,000		$ 24,300,000
Revolving Credit Facility | Deerfield Revolver | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	4.60%
Variable rate, floor	1.00%
Letter of Credit | Bank of America
Line of Credit Facility [Line Items]
Aggregate maximum borrowing capacity						$ 10,000,000
Term of line of credit						2 years
Termination notice period												3 days
TriVascular Technologies, Inc.
Line of Credit Facility [Line Items]
Equity consideration issued in merger (in shares) | shares				13,586,503
Minimum | Revolving Credit Facility | Bank of America
Line of Credit Facility [Line Items]
Liquidation proceeds, monetary amount												$ 30,000,000
Other Assets | Accounting Standards Update 2015-03 | Revolving Credit Facility | MidCap
Line of Credit Facility [Line Items]
Debt issuance costs, net									900,000	900,000		900,000
Long-term Debt | Accounting Standards Update 2015-03 | Revolving Credit Facility | MidCap
Line of Credit Facility [Line Items]
Debt issuance costs, net									$ (900,000)	$ (900,000)		$ (900,000)
Facility Agreement | Deerfield Warrants
Line of Credit Facility [Line Items]
Expiration date of warrants issued												7 years
Warrant exercise limitation threshold												4.985%
Facility Agreement | Common Stock | Deerfield Warrants
Line of Credit Facility [Line Items]
Debt issuance costs	$ 400,000
Shares in which warrants can be converted (in shares) | shares	6,470,000
Exercise price of warrants issued (in dollars per share) | $ / shares	$ 9.23
Fair value of warrants	$ 14,300,000
3.25% Convertible Senior Notes | Other Assets | Accounting Standards Update 2015-03
Line of Credit Facility [Line Items]
Debt issuance costs, net																$ 2,900,000
Convertible Debt
Line of Credit Facility [Line Items]
Reclassification of conversion features to derivative liabilities								$ 24,800,000
Convertible Debt | 2.25% Convertible Senior Notes
Line of Credit Facility [Line Items]
Debt instrument face amount							$ 86,250,000
Stated interest rate							2.25%		2.25%	2.25%		2.25%
Proceeds from convertible debt							$ 82,600,000
Redemption price percentage												100.00%
Conversion of convertible securities												41.6051
Convertible conversion price (in dollars per share) | $ / shares							$ 24.04		$ 24.04	$ 24.04		$ 24.04
Violation or event of default, declaration by note holders, percentage												25.00%
Fair value disclosure							$ 66,900,000
Beneficial conversion feature	(2,200,000)						19,300,000
Unamortized discount							3,700,000
Repurchased debt amount	68,000,000
Non-cash loss on debt extinguishment	3,200,000
Convertible notes							$ 86,300,000		$ 18,300,000	$ 18,300,000		$ 18,300,000
Deferred finance costs, noncurrent, net									200,000	200,000		200,000
Periodic principal payment												0
Cap price (in dollars per security) | $ / security							29.02
Convertible Debt | 2.25% Convertible Senior Notes | Minimum
Line of Credit Facility [Line Items]
Periodic interest payment												1,100,000
Convertible Debt | 2.25% Convertible Senior Notes | Maximum
Line of Credit Facility [Line Items]
Periodic interest payment												$ 1,500,000
Convertible Debt | 2.25% Convertible Senior Notes | Other Assets
Line of Credit Facility [Line Items]
Unamortized discount							$ 2,900,000
Convertible Debt | 2.25% Convertible Senior Notes | Other Assets | Accounting Standards Update 2015-03
Line of Credit Facility [Line Items]
Debt issuance costs, net																1,900,000
Convertible Debt | 2.25% Convertible Senior Notes | Additional Paid-in Capital
Line of Credit Facility [Line Items]
Unamortized discount							$ 800,000
Convertible Debt | 2.25% Convertible Senior Notes | Long-term Debt | Accounting Standards Update 2015-03
Line of Credit Facility [Line Items]
Debt issuance costs, net																(1,900,000)
Convertible Debt | 2.25% Convertible Senior Notes | Redemption, Period One
Line of Credit Facility [Line Items]
Threshold trading days | d												20
Threshold consecutive trading days | d												30
Threshold percentage of stock price trigger												130.00%
Redemption price percentage												100.00%
Convertible Debt | 2.25% Convertible Senior Notes | Redemption, Period Two
Line of Credit Facility [Line Items]
Threshold trading days | d												20
Threshold consecutive trading days | d												5
Threshold percentage of stock price trigger												98.00%
Threshold consecutive business days												30 days
Threshold business days | d												5
Convertible Debt | 3.25% Convertible Senior Notes
Line of Credit Facility [Line Items]
Debt instrument face amount					$ 125,000,000.0
Stated interest rate					3.25%
Threshold consecutive trading days | d												30
Redemption price percentage												100.00%
Conversion of convertible securities					89.4314
Convertible conversion price (in dollars per share) | $ / shares					$ 11.18
Fair value disclosure					$ 97,800,000
Beneficial conversion feature					27,200,000
Unamortized discount					2,900,000
Convertible notes									105,500,000	105,500,000		$ 105,500,000					$ 125,000,000
Periodic principal payment												$ 0
Holding threshold required to declare debt due												25.00%
Debt issuance costs									$ 2,100,000	$ 2,100,000		$ 2,100,000
Convertible Debt | 3.25% Convertible Senior Notes | Convertible Condition One
Line of Credit Facility [Line Items]
Threshold trading days | d												20
Threshold consecutive trading days | d												30
Threshold percentage of stock price trigger												130.00%
Convertible Debt | 3.25% Convertible Senior Notes | Convertible Condition Two
Line of Credit Facility [Line Items]
Threshold percentage of stock price trigger												98.00%
Threshold consecutive business days												5 days
Threshold business days | d												5
Convertible Debt | 3.25% Convertible Senior Notes | Convertible Condition Three
Line of Credit Facility [Line Items]
Threshold trading days | d												2
Convertible Debt | 3.25% Convertible Senior Notes | Minimum
Line of Credit Facility [Line Items]
Periodic interest payment												$ 9,100,000
Convertible Debt | 3.25% Convertible Senior Notes | Maximum
Line of Credit Facility [Line Items]
Periodic interest payment												$ 10,700,000
Convertible Debt | 3.25% Convertible Senior Notes | Other Assets
Line of Credit Facility [Line Items]
Unamortized discount					3,700,000
Convertible Debt | 3.25% Convertible Senior Notes | Additional Paid-in Capital
Line of Credit Facility [Line Items]
Unamortized discount					$ 800,000
Convertible Debt | 3.25% Convertible Senior Notes | Long-term Debt | Accounting Standards Update 2015-03
Line of Credit Facility [Line Items]
Debt issuance costs, net																$ (2,900,000)
Convertible Debt | 3.25% Convertible Senior Notes | Redemption, Period One
Line of Credit Facility [Line Items]
Threshold trading days | d												30
Convertible Debt | 3.25% Convertible Senior Notes | Redemption, Period Two
Line of Credit Facility [Line Items]
Threshold trading days | d												2
Secured Debt | Facility Agreement
Line of Credit Facility [Line Items]
Debt instrument face amount	120,000,000.0
Stated interest rate									6.87%	6.87%		6.87%
Deferred finance costs, noncurrent, net	$ 5,100,000								$ 4,900,000	$ 4,900,000		$ 4,900,000
Yield enhancement fee	2.25%
Periodic amortization payment	$ 40,000,000
Amount outstanding									$ 105,300,000	$ 105,300,000		105,300,000
Secured Debt | Facility Agreement | Minimum
Line of Credit Facility [Line Items]
Periodic interest payment												1,400,000
Secured Debt | Facility Agreement | Maximum
Line of Credit Facility [Line Items]
Periodic interest payment												$ 8,400,000