Credit Facilities (Details)					1 Months Ended	3 Months Ended			9 Months Ended
	Jul. 29, 2016 USD ($)	Feb. 03, 2016 shares	Nov. 02, 2015 USD ($) $ / shares	Dec. 10, 2013 USD ($) $ / shares $ / security	Feb. 29, 2016 USD ($)	Sep. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) d $ / shares shares	Sep. 30, 2015 USD ($)	Jul. 11, 2016 USD ($)	Jun. 02, 2016 shares	Dec. 31, 2015 USD ($) shares	Nov. 30, 2015 USD ($)	Jul. 21, 2015 USD ($)
Line of Credit Facility [Line Items]
Convertible notes						$ 174,734,000			$ 174,734,000				$ 167,748,000
Payments of derivative issuance costs				$ 7,400,000
Change in fair value of derivative liabilities						$ 0		$ 0	$ 43,831,000	$ 0
Common stock authorized (in shares) | shares						135,000,000			135,000,000			100,000,000	135,000,000
Adjustments to additional paid-in capital, conversion features of Senior Notes							$ 68,600,000
Restricted cash						$ 2,000,000			$ 2,000,000
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 | Japan Lifeline Co., Ltd.
Line of Credit Facility [Line Items]
Stated interest rate											1.50%
Amount outstanding											$ 6,000,000
Revolving Credit Facility | MidCap
Line of Credit Facility [Line Items]
Debt issuance costs, net						900,000			$ 900,000
Aggregate maximum borrowing capacity	$ 50,000,000.0
Amount outstanding						$ 0			$ 0
Interest rate at end of period						4.60%			4.60%
Maximum amount on which fees are calculated	$ 10,000,000
Unused line fee	0.50%
Collateral management fee	0.50%
Deferred financing costs						$ 900,000			$ 900,000
Letter of Credit | Bank of America
Line of Credit Facility [Line Items]
Aggregate maximum borrowing capacity															$ 10,000,000
Convertible Debt
Line of Credit Facility [Line Items]
Reclassification of conversion features to derivative liabilities					$ 24,800,000
2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Debt instrument face amount				86,250,000
Stated interest rate						2.25%			2.25%
Proceeds from convertible debt				82,600,000
Conversion of convertible securities									41.6051
Redemption price percentage									100.00%
Violation or event of default, declaration by note holders, percentage									25.00%
Fair value disclosure				66,900,000
Beneficial conversion feature				19,300,000
Unamortized discount				3,700,000
Convertible notes				$ 86,300,000		$ 76,800,000			$ 76,800,000
Deferred finance costs, noncurrent, net						$ 1,500,000			$ 1,500,000
Convertible conversion price | $ / shares				$ 24.04		$ 24.04			$ 24.04
Cap price | $ / security				29.02
3.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Debt instrument face amount			$ 125,000,000.0
Stated interest rate						3.25%			3.25%
Threshold trading days | d									20
Threshold consecutive trading days									30 days
Threshold consecutive business days									5 days
Threshold percentage of stock price trigger									130.00%
Threshold business days | d									5
Conversion of convertible securities			89.4314
Redemption price percentage			98.00%						100.00%
Fair value disclosure			$ 97,800,000
Beneficial conversion feature			27,200,000
Unamortized discount			$ 2,900,000
Convertible notes						$ 101,900,000			$ 101,900,000					$ 125,000,000
Deferred finance costs, noncurrent, net						$ 2,500,000			$ 2,500,000
Convertible conversion price | $ / shares			$ 11.18
Redemption, Period One | 2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Threshold trading days | d									20
Threshold consecutive trading days									30 days
Threshold percentage of stock price trigger									130.00%
Redemption price percentage									100.00%
Redemption, Period Two | 2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Threshold trading days | d									20
Threshold consecutive trading days									5 years
Threshold consecutive business days									30 days
Threshold percentage of stock price trigger									98.00%
Threshold business days | d									5
Other Assets | 2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Unamortized discount				$ 2,900,000
Other Assets | 3.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Unamortized discount			$ 3,700,000
Additional Paid-in Capital | 2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Unamortized discount				$ 800,000
Additional Paid-in Capital | 3.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Unamortized discount			$ 800,000
Minimum | Revolving Credit Facility | Bank of America
Line of Credit Facility [Line Items]
Liquidation proceeds, monetary amount									$ 30,000,000
Minimum | 2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Periodic interest payment									5,700,000
Minimum | 3.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Periodic interest payment									9,100,000
Maximum | 2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Periodic interest payment									6,900,000
Maximum | 3.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Periodic interest payment									$ 10,700,000
Accounting Standards Update 2015-03 | Other Assets | 2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Debt issuance costs, net													$ (1,900,000)
Accounting Standards Update 2015-03 | Other Assets | 3.25% Convertible Senior Notes
Line of Credit Facility [Line Items]
Debt issuance costs, net													(2,900,000)
Accounting Standards Update 2015-03 | Long-term Debt | 2.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Debt issuance costs, net													1,900,000
Accounting Standards Update 2015-03 | Long-term Debt | 3.25% Convertible Senior Notes | Convertible Debt
Line of Credit Facility [Line Items]
Debt issuance costs, net													$ 2,900,000
TriVascular Technologies, Inc.
Line of Credit Facility [Line Items]
Equity consideration issued in merger (in shares) | shares		13,586,503
LIBOR | Revolving Credit Facility | MidCap
Line of Credit Facility [Line Items]
Basis spread on variable rate	4.10%
Variable rate, maximum	0.50%