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Other Consolidated Financial Statement (Details Textual) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Gain (loss) on investments, net	$ (82.1)		$ (4.1)	$ (52.6)	$ 198.9
Other long-term liabilities	1,428.1			1,428.1		$ 1,348.9
Accrued income taxes	729.3			729.3		$ 803.3
Net gains recognized on the increase in fair value of equity securities	(82.3)		$ (9.0)	(40.3)	150.5
Proceeds from sale of available-for-sale securities, equity				0.5	$ 476.0
Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Income Tax Expense		$ 697.0		$ 635.0
Ionis
Class of Stock [Line Items]
Net gains recognized on the increase in fair value of equity securities	66.2
Denali Therapeutics
Class of Stock [Line Items]
Net gains recognized on the increase in fair value of equity securities	(29.6)
Sangamo
Class of Stock [Line Items]
Net gains recognized on the increase in fair value of equity securities	$ 15.2