Condensed Consolidated Statements Of Operations And Comprehensive (Loss) Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues:
Total revenues	$ 258.5	$ 222.1	$ 798.0	$ 544.0
Operating expenses:
Cost of sales	2.7	2.2	7.2	4.9
Research and development	69.1	45.3	208.3	144.7
Acquired in-process research and development	118.5	0.0	164.5	118.1
Selling, general and administrative	112.5	84.5	326.8	252.8
Total operating expenses	302.8	132.0	706.8	520.5
Operating (loss) income	(44.3)	90.1	91.2	23.5
Other (expense) income:
Interest expense	(8.5)	(8.0)	(25.0)	(23.8)
Unrealized loss on equity securities	(7.0)	(28.5)	(12.2)	(5.8)
Investment income and other, net	2.7	4.8	11.0	14.0
Total other expense, net	(12.8)	(31.7)	(26.2)	(15.6)
(Loss) income before provision for income taxes	(57.1)	58.4	65.0	7.9
Provision for income taxes	0.5	4.6	5.6	4.9
Net (loss) income	(57.6)	53.8	59.4	3.0
Unrealized (loss) gain on debt securities available-for-sale, net of tax	(1.4)	1.0	1.8	3.6
Comprehensive (loss) income	$ (59.0)	$ 54.8	$ 61.2	$ 6.6
Net (loss) income per share, basic (in USD per share)	$ (0.62)	$ 0.59	$ 0.64	$ 0.03
Net (loss) income per share, diluted (in USD per share)	$ (0.62)	$ 0.56	$ 0.61	$ 0.03
Weighted average common shares outstanding, basic (in shares)	93.3	91.9	93.0	91.4
Weighted average common shares outstanding, diluted (in shares)	93.3	96.1	98.0	95.2
Product sales, net
Revenues:
Total revenues	$ 254.1	$ 198.1	$ 752.8	$ 515.0
Collaboration revenue
Revenues:
Total revenues	$ 4.4	$ 24.0	$ 45.2	$ 29.0