Long-term debt	12 Months Ended
Dec. 31, 2017
Long-term debt [Abstract]
Long-term debt	10. Long-term debt 2.875% Convertible senior notes due 2021 On January 29, 2014, the Company issued $250.0 million aggregate principal amount of 2.875% Convertible Senior Notes due 2021 (the "Notes"). The Notes bear interest at a rate of 2.875% per year, payable semi-annually in arrears on January 15 and July 15 of each year. The Notes mature on January 15, 2021, unless earlier purchased by the Company or converted. The original conversion rate is equal to 30.8821 shares of common stock per $1,000 principal amount of notes (which is equivalent to a conversion price of approximately $32.38 per share of common stock). The conversion rate is subject to adjustment upon the occurrence of certain specified events but will not be adjusted for accrued and unpaid interest. The Company incurred approximately $8.3 million in debt issuance costs associated with the Notes, which has been capitalized on the consolidated balance sheets and is being amortized over seven years. As of August 1, 2016, certain conversion features were triggered due to the completion of the Aptevo spin-off. The conversion rate under the Notes was adjusted in accordance with the terms of the indenture. Effective August 12, 2016, the conversion rate was adjusted to 32.3860 shares of common stock per $1,000 principal amount of notes (which is equivalent to a conversion price of approximately $30.88 per share of common stock). On November 14, 2017, the Company issued a notice of termination of conversion rights for its outstanding Notes, of which $250.0 million was outstanding as of the notice date. In connection with the notice of termination, bondholders were given the option to convert their notes into the Company's stock at a rate of 32.386 per $1,000 of principal outstanding, plus a make-whole of an additional 3.1556 shares per $1,000 principal outstanding, in accordance with the terms of the indenture. The Company was not obligated to pay accrued or unpaid interest on converted notes, and bondholders who did not convert by the deadline of December 28, 2017 would retain their bonds but lose the conversion rights associated with the Notes and be paid interest of 2.875% until the earlier of maturity of the Notes in 2021 or the bonds being called and repaid in full by the Company. Between July 15, 2017 and the notification of termination of conversion rights, the Company accrued interest on the converted Notes of $2.4 million which was recorded as an increase in additional paid-in-capital on the balance sheet. Between November 14, 2017 and December 28, 2017 (the "conversion period"), approximately $239.4 million of bonds were converted into 8.5 million shares of the Company's common stock, inclusive of shares issued as part of the make-whole provision. In addition, the Company recorded a reduction in additional paid-in-capital on the Company's balance sheet of $3.6 million associated with debt issuance costs attributable to the converted notes. After giving effect to the converted bonds, the outstanding principal balance of the Notes as of December 31, 2017 was $10.6 million. Senior secured credit agreement On September 29, 2017, the Company entered into a senior secured credit agreement (the "2017 Credit Agreement") with four lending financial institutions, which replaced the Company's prior senior secured credit agreement (the "2013 Credit Agreement"). The 2017 Credit Agreement provides for a senior secured credit facility of up to $200 million through September 29, 2022. The 2017 Credit Agreement also includes a $100 million accordion feature, which could provide an additional $100 million in revolver or incremental term loans, at the option of the Company, resulting in a potential aggregate commitment of up to $300 million, subject to certain conditions and requirements set forth in the 2017 Credit Agreement. As of December 31, 2017, no amounts were drawn under the 2017 Credit Agreement. The Company's payment obligations under the 2017 Credit Agreement are secured by a lien on substantially all of the Company's assets, including the stock of all the Company's domestic subsidiaries, and the assets of the subsidiary guarantors. Borrowings under the 2017 Credit Agreement will bear interest at a rate per annum equal to (a) a eurocurrency rate plus a margin ranging from 1.50% to 2.50% per annum, depending on the Company's consolidated net leverage ratio or (b) a base rate (which is the highest of the prime rate, the federal funds rate plus 0.50% and a eurocurrency rate for an interest period of one month plus 1%) plus a margin ranging from 0.50% to 1.50%, depending on the Company's consolidated net leverage ratio. The Company is required to make quarterly payments under the 2017 Credit Agreement of accrued and unpaid interest on the outstanding principal balance, based on the above interest rates. In addition, the Company is required to pay commitment fees ranging from 0.25% to 0.40% per annum, depending on the Company's consolidated net leverage ratio, in respect of daily unused commitments under the 2017 Credit Agreement. The 2017 Credit Agreement contains affirmative and negative covenants customary for financings of this type. Negative covenants in the 2017 Credit Agreement, among other things, limit the Company's ability to incur indebtedness and liens; dispose of assets; make investments including loans, advances, guarantees, or acquisitions (other than permitted acquisitions, subject to compliance with the financial covenants and certain other conditions); and enter into certain mergers or consolidation transactions. The 2017 Credit Agreement also contains financial covenants, tested quarterly and in connection with any triggering events under the 2017 Credit Agreement: (1) a minimum consolidated debt service coverage ratio of 2.50 to 1.00, and (2) a maximum consolidated net leverage ratio of 3.50 to 1.00, which may be adjusted to 4.00 to 1.00 for a four-quarter period in connection with a permitted acquisition, subject to the terms and conditions of the 2017 Credit Agreement. Each of the ratios referred to in the foregoing clauses (1) and (2) is calculated on a consolidated basis for each consecutive four fiscal quarter periods. As of December 31, 2017, the Company is compliance with affirmative and negative covenants. The Company entered into a standby letter of credit and guarantee arrangement with a bank in the amount of $1.0 million that is fully collateralized by cash, which is classified as restricted cash in the Company's consolidated balance sheet.

10. Long-term debt

2.875% Convertible senior notes due 2021

On January 29, 2014, the Company issued $250.0 million aggregate principal amount of 2.875% Convertible Senior Notes due 2021 (the "Notes"). The Notes bear interest at a rate of 2.875% per year, payable semi-annually in arrears on January 15 and July 15 of each year. The Notes mature on January 15, 2021, unless earlier purchased by the Company or converted. The original conversion rate is equal to 30.8821 shares of common stock per $1,000 principal amount of notes (which is equivalent to a conversion price of approximately $32.38 per share of common stock). The conversion rate is subject to adjustment upon the occurrence of certain specified events but will not be adjusted for accrued and unpaid interest. The Company incurred approximately $8.3 million in debt issuance costs associated with the Notes, which has been capitalized on the consolidated balance sheets and is being amortized over seven years. As of August 1, 2016, certain conversion features were triggered due to the completion of the Aptevo spin-off. The conversion rate under the Notes was adjusted in accordance with the terms of the indenture. Effective August 12, 2016, the conversion rate was adjusted to 32.3860 shares of common stock per $1,000 principal amount of notes (which is equivalent to a conversion price of approximately $30.88 per share of common stock).

On November 14, 2017, the Company issued a notice of termination of conversion rights for its outstanding Notes, of which $250.0 million was outstanding as of the notice date. In connection with the notice of termination, bondholders were given the option to convert their notes into the Company's stock at a rate of 32.386 per $1,000 of principal outstanding, plus a make-whole of an additional 3.1556 shares per $1,000 principal outstanding, in accordance with the terms of the indenture. The Company was not obligated to pay accrued or unpaid interest on converted notes, and bondholders who did not convert by the deadline of December 28, 2017 would retain their bonds but lose the conversion rights associated with the Notes and be paid interest of 2.875% until the earlier of maturity of the Notes in 2021 or the bonds being called and repaid in full by the Company. Between July 15, 2017 and the notification of termination of conversion rights, the Company accrued interest on the converted Notes of $2.4 million which was recorded as an increase in additional paid-in-capital on the balance sheet. Between November 14, 2017 and December 28, 2017 (the "conversion period"), approximately $239.4 million of bonds were converted into 8.5 million shares of the Company's common stock, inclusive of shares issued as part of the make-whole provision. In addition, the Company recorded a reduction in additional paid-in-capital on the Company's balance sheet of $3.6 million associated with debt issuance costs attributable to the converted notes. After giving effect to the converted bonds, the outstanding principal balance of the Notes as of December 31, 2017 was $10.6 million.

Senior secured credit agreement

On September 29, 2017, the Company entered into a senior secured credit agreement (the "2017 Credit Agreement") with four lending financial institutions, which replaced the Company's prior senior secured credit agreement (the "2013 Credit Agreement"). The 2017 Credit Agreement provides for a senior secured credit facility of up to $200 million through September 29, 2022. The 2017 Credit Agreement also includes a $100 million accordion feature, which could provide an additional $100 million in revolver or incremental term loans, at the option of the Company, resulting in a potential aggregate commitment of up to $300 million, subject to certain conditions and requirements set forth in the 2017 Credit Agreement. As of December 31, 2017, no amounts were drawn under the 2017 Credit Agreement.

The Company's payment obligations under the 2017 Credit Agreement are secured by a lien on substantially all of the Company's assets, including the stock of all the Company's domestic subsidiaries, and the assets of the subsidiary guarantors. Borrowings under the 2017 Credit Agreement will bear interest at a rate per annum equal to (a) a eurocurrency rate plus a margin ranging from 1.50% to 2.50% per annum, depending on the Company's consolidated net leverage ratio or (b) a base rate (which is the highest of the prime rate, the federal funds rate plus 0.50% and a eurocurrency rate for an interest period of one month plus 1%) plus a margin ranging from 0.50% to 1.50%, depending on the Company's consolidated net leverage ratio. The Company is required to make quarterly payments under the 2017 Credit Agreement of accrued and unpaid interest on the outstanding principal balance, based on the above interest rates. In addition, the Company is required to pay commitment fees ranging from 0.25% to 0.40% per annum, depending on the Company's consolidated net leverage ratio, in respect of daily unused commitments under the 2017 Credit Agreement.

The 2017 Credit Agreement contains affirmative and negative covenants customary for financings of this type. Negative covenants in the 2017 Credit Agreement, among other things, limit the Company's ability to incur indebtedness and liens; dispose of assets; make investments including loans, advances, guarantees, or acquisitions (other than permitted acquisitions, subject to compliance with the financial covenants and certain other conditions); and enter into certain mergers or consolidation transactions. The 2017 Credit Agreement also contains financial covenants, tested quarterly and in connection with any triggering events under the 2017 Credit Agreement: (1) a minimum consolidated debt service coverage ratio of 2.50 to 1.00, and (2) a maximum consolidated net leverage ratio of 3.50 to 1.00, which may be adjusted to 4.00 to 1.00 for a four-quarter period in connection with a permitted acquisition, subject to the terms and conditions of the 2017 Credit Agreement. Each of the ratios referred to in the foregoing clauses (1) and (2) is calculated on a consolidated basis for each consecutive four fiscal quarter periods. As of December 31, 2017, the Company is compliance with affirmative and negative covenants.

The Company entered into a standby letter of credit and guarantee arrangement with a bank in the amount of $1.0 million that is fully collateralized by cash, which is classified as restricted cash in the Company's consolidated balance sheet.