Other Investments	9 Months Ended
Other Investments	Sep. 30, 2020
Investments, All Other Investments [Abstract]
Other Investments	Other Investments Other investments include strategic investments in equity securities of certain biotechnology companies which we acquired in connection with strategic business development transactions, including license and option agreements. These investments are included in other assets in our condensed consolidated balance sheets. Moderna During 2014, we purchased $37.5 of preferred stock of Moderna Therapeutics, Inc. (Moderna), a privately held biotechnology company, which was initially recorded at cost. We began recording the investment at fair value, with the effects of a holding period restriction estimated using an option pricing valuation model, upon Moderna's completion of its initial public offering (IPO) in 2018. During the three and nine months ended September 30, 2019, we recognized an unrealized gain of $12.3 and $13.1, respectively, in investment income to adjust our investment in Moderna to fair value. On December 9, 2019, we sold our investment in Moderna for $114.7 in net proceeds, resulting in a realized gain of $77.2 on our initial investment. Dicerna In October 2018, we purchased $10.3 of Dicerna Pharmaceuticals Inc. (Dicerna) common stock in connection with an agreement that we entered into with Dicerna, a publicly-traded biopharmaceutical company. As our equity investment in Dicerna common stock has a readily determinable fair value, we are recording the investment at fair value. During the three and nine months ended September 30, 2020, we recognized an unrealized loss of $6.2 and $3.4, respectively, in investment income to adjust our equity investment in Dicerna to fair value. During the three and nine months ended September 30, 2019, we recognized an unrealized loss of $1.1 and unrealized gain of $3.1, respectively, in investment income to adjust our equity investment in Dicerna to fair value. The fair value of this investment was $15.0 and $18.4 as of September 30, 2020 and December 31, 2019, respectively. Caelum In January 2019, we purchased $41.0 of preferred stock of Caelum Biosciences (Caelum), a privately-held biotechnology company, and a $16.1 option to acquire the remaining equity in Caelum, based on Phase II data, in connection with an agreement that we entered into with Caelum. Following discussions with the FDA, Caelum changed its clinical development plan for CAEL-101 in the fourth quarter 2019. A Phase II trial for CAEL-101 subsequently commenced during the first quarter of 2020 and met its primary objectives, supporting the safety and tolerability of CAEL-101 and confirmed the dose and regimen to be adopted for the Phase III studies. In December 2019, we amended the terms of the agreement with respect to the option to acquire the remaining equity in Caelum based on data from the modified Phase II/III trials. We accounted for the amendment as an exchange transaction as the terms of the modified option were determined to be substantially different than the terms of the original option. In conjunction with this amendment, we recognized a gain of $32.0 during the fourth quarter 2019 in other income and (expense), which reflects an increase in the fair value of the option, less $20.0 in incremental upfront funding which we accrued as of December 31, 2019 and paid during the first quarter 2020, and $4.1 associated with the change in the fair value of contingent payments which we also modified as part of the amendment. See Note 16, Commitments and Contingencies, for additional information on the agreement. As our equity investment in Caelum and the option to acquire the remaining equity in Caelum do not have a readily determinable fair value, we only adjust the carrying value of the assets for impairment and any subsequent changes resulting from an observable price change in an orderly transaction for identical or similar equity securities of the same issuer. There were no observable price changes associated with these assets during the three and nine months ended September 30, 2020 and 2019. As of September 30, 2020, the carrying value of the investment and option, respectively, was $41.0 and $64.0. As of December 31, 2019, the carrying value of the investment and option, respectively, was $41.0 and $64.0. The investment and option were not impaired as of September 30, 2020. Zealand In March 2019, we purchased $13.8 of Zealand Pharma A/S (Zealand) common stock in connection with an agreement that we entered into with Zealand, a publicly-traded biopharmaceutical company based in Copenhagen, Denmark. See Note 16, Commitments and Contingencies, for additional information on the agreement. As our equity investment in Zealand common stock has a readily determinable fair value, we are recording the investment at fair value. During the three and nine months ended September 30, 2020, we recognized an unrealized gain of $1.8 and $0.8, respectively, in investment income to adjust our equity investment in Zealand to fair value. During the three and nine months ended September 30, 2019, we recognized an unrealized gain of $3.7 and $7.3, respectively, in investment income to adjust our equity investment in Zealand to fair value. The fair value of this investment was $30.5 and $28.5 as of September 30, 2020 and December 31, 2019, respectively. Eidos In September 2019, we purchased $19.9 of Eidos Therapeutics, Inc. (Eidos) common stock, in connection with an agreement that we entered into with Eidos, a publicly-traded biopharmaceutical company and subsidiary of BridgeBio Pharma, Inc. See Note 16, Commitments and Contingencies, for additional information on the agreement. As our equity investment in Eidos common stock has a readily determinable fair value, we are recording the investment at fair value. During the three and nine months ended September 30, 2020, we recognized an unrealized gain of $3.4 and $0.3, respectively, in investment income to adjust our equity investment in Eidos to fair value. During the three and nine months ended September 30, 2019, we recognized an unrealized loss of $2.9, in investment income to adjust our equity investment in Eidos to fair value. The fair value of this investment was $28.1 and $27.8 as of September 30, 2020 and December 31, 2019, respectively. Stealth In October 2019, we purchased $9.6 of Stealth BioTherapeutics Corp. (Stealth) common stock, in connection with an agreement that we entered into with Stealth, a publicly traded clinical-stage biotechnology company. As our equity investment in Stealth common stock has a readily determinable fair value, we are recording the investment at fair value. During the three and nine months ended September 30, 2020, we recognized an unrealized loss of $0.7 and $2.6, respectively, in investment income to adjust our equity investment in Stealth to fair value. The fair value of this investment was $1.8 and $4.4 as of September 30, 2020 and December 31, 2019, respectively. Portola In March 2020 and April 2020, we purchased $14.5 and $3.6, respectively, of common stock of Portola Pharmaceuticals, Inc., a publicly traded commercial-stage biological company which we acquired on July 2, 2020. As our equity investment in Portola common stock had a readily determinable fair value, we recorded the investment at fair value. During the three and nine months ended September 30, 2020, we recognized a net gain of $0.1 and $29.7 in investment income, respectively, relating to our Portola investment. Upon the closing of the acquisition of Portola on July 2, 2020, the fair value of the equity investment of $47.8 was derecognized and included in the fair value of consideration transferred, resulting in a realized gain of $29.7 on our initial investment. Inozyme On July 17, 2020, we sold certain intellectual property rights and assets focusing on ENPP1 gene deficiencies to Inozyme Pharma (Inozyme), a publicly traded biopharmaceutical company, in exchange for $14.8 of Inozyme Pharma common stock, which was initially recorded at its IPO offering price, net of the effects of a nine month holding period restriction. We recognized the $14.8 of consideration received as a gain within gain on sale of asset in our condensed consolidated statement of operations. As our equity investment in Inozyme common stock has a readily determinable fair value, we are recording the investment at fair value, with the effects of a nine month holding period restriction estimated using an option pricing valuation model. During the three and nine months ended September 30, 2020, we recognized an unrealized gain of $10.2, in investment income to adjust our investment to fair value. The fair value of this investment was $25.0 as of September 30, 2020.