CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 624.6	$ 461.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	56.1	51.0
Non-cash compensation expense	105.8	107.9
Other non-cash items, net	82.6	(23.8)
Deferred taxes	9.9	(10.7)
Changes in assets and liabilities:
Increase in Sanofi, trade, and other accounts receivable	(169.0)	(91.1)
Increase in inventories	(70.8)	(58.6)
Decrease in prepaid expenses and other assets	70.1	54.3
Increase in deferred revenue	73.9	81.1
(Decrease) increase in accounts payable, accrued expenses, and other liabilities	(85.2)	325.8
Total adjustments	73.4	435.9
Net cash provided by operating activities	698.0	897.0
Cash flows from investing activities:
Purchases of marketable and other securities	(714.3)	(1,040.2)
Sales or maturities of marketable securities	441.2	338.4
Capital expenditures	(170.1)	(74.3)
Net cash used in investing activities	(443.2)	(776.1)
Cash flows from financing activities:
Proceeds from issuance of Common Stock	811.4	140.6
Payments in connection with Common Stock tendered for employee tax obligations	(155.1)	(10.7)
Repurchases of Common Stock	(320.7)	(10.0)
Net cash provided by financing activities	335.6	119.9
Net increase in cash, cash equivalents, and restricted cash	590.4	240.8
Cash, cash equivalents, and restricted cash at beginning of period	1,630.3	1,480.2
Cash, cash equivalents, and restricted cash at end of period	$ 2,220.7	$ 1,721.0