CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 461.1	$ 478.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	51.0	36.4
Non-cash compensation expense	107.9	82.4
Other non-cash items, net	(23.8)	(4.2)
Deferred taxes	(10.7)	(6.4)
Changes in assets and liabilities:
(Increase) decrease in Sanofi, Bayer, and trade accounts receivable	(106.1)	30.4
Increase in inventories	(58.6)	(88.8)
Decrease in prepaid expenses and other assets	69.3	68.8
Increase (decrease) in deferred revenue	426.5	(54.5)
(Decrease) increase in accounts payable, accrued expenses, and other liabilities	(19.6)	76.7
Total adjustments	435.9	140.8
Net cash provided by operating activities	897.0	618.8
Cash flows from investing activities:
Purchases of marketable and other securities	(1,040.2)	(601.3)
Sales or maturities of marketable securities	338.4	255.3
Capital expenditures	(74.3)	(79.4)
Net cash used in investing activities	(776.1)	(425.4)
Cash flows from financing activities:
Proceeds from issuance of Common Stock	140.6	13.4
Payments in connection with Common Stock tendered for employee tax obligations	(10.7)	0.0
Repurchases of Common Stock	(10.0)	0.0
Net cash provided by financing activities	119.9	13.4
Net increase in cash, cash equivalents, and restricted cash	240.8	206.8
Cash, cash equivalents, and restricted cash at beginning of period	1,480.2	825.2
Cash, cash equivalents, and restricted cash at end of period	$ 1,721.0	$ 1,032.0