Condensed Consolidated Statements of Changes in Stockholder's Equity Statement - USD ($) shares in Millions, $ in Millions	Total	Adoption of new accounting standards	Common Stock	Additional Paid-In Capital	Treasury Stock at Cost	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Adoption of new accounting standards
Balances, common shares at Dec. 31, 2018			236.2
Balances, value at Dec. 31, 2018	$ 9,165.3	$ (90.3)	$ 0.0	$ 8,539.1	$ (1,689.9)	$ (9.7)	$ 2,325.8	$ (90.3)
Balances, treasury shares at Dec. 31, 2018					12.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock, shares	0.4				0.4
Repurchase of common stock	$ (48.9)				$ (48.9)
Issuance of common stock under stock option and stock purchase plans, shares			0.2
Issuance of common stock under stock option and stock purchase plans	21.3			21.3
Issuance of restricted common stock, shares			0.9
Issuance of restricted common stock	0.0
Share-based compensation expense	116.6			116.6
Net (loss) income	1,047.7						1,047.7
Other comprehensive loss	(48.2)					(48.2)
Balances, treasury shares at Jun. 30, 2019					13.1
Balances, value at Jun. 30, 2019	10,163.5		$ 0.0	8,677.0	$ (1,738.8)	(57.9)	3,283.2
Balances, common shares at Jun. 30, 2019			237.3
Balances, common shares at Mar. 31, 2019			237.0
Balances, value at Mar. 31, 2019	$ 9,706.6		$ 0.0	8,604.9	$ (1,701.2)	(20.5)	2,823.4
Balances, treasury shares at Mar. 31, 2019					12.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock, shares	0.3				0.3
Repurchase of common stock	$ (37.6)				$ (37.6)
Issuance of common stock under stock option and stock purchase plans, shares			0.1
Issuance of common stock under stock option and stock purchase plans	11.2			11.2
Issuance of restricted common stock, shares			0.2
Issuance of restricted common stock	0.0
Share-based compensation expense	60.9			60.9
Net (loss) income	459.8						459.8
Other comprehensive loss	(37.4)					(37.4)
Balances, treasury shares at Jun. 30, 2019					13.1
Balances, value at Jun. 30, 2019	10,163.5		$ 0.0	8,677.0	$ (1,738.8)	(57.9)	3,283.2
Balances, common shares at Jun. 30, 2019			237.3
Balances, common shares at Dec. 31, 2019			237.8
Balances, value at Dec. 31, 2019	$ 11,271.8		$ 0.0	8,804.7	$ (2,105.9)	(66.8)	4,639.8
Balances, treasury shares at Dec. 31, 2019	16.5				16.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock, shares	3.6				3.6
Repurchase of common stock	$ (360.8)				$ (360.8)
Issuance of common stock under stock option and stock purchase plans, shares			0.2
Issuance of common stock under stock option and stock purchase plans	12.9			12.9
Issuance of restricted common stock, shares			1.2
Issuance of restricted common stock	0.0
Share-based compensation expense	121.5			124.8	$ (3.3)
Net (loss) income	(510.5)						(510.5)
Other comprehensive loss	$ (44.1)					(44.1)
Balances, treasury shares at Jun. 30, 2020	20.1				20.1
Balances, value at Jun. 30, 2020	$ 10,490.8		$ 0.0	8,942.4	$ (2,470.0)	(110.9)	4,129.3
Balances, common shares at Jun. 30, 2020			239.2
Balances, common shares at Mar. 31, 2020			238.9
Balances, value at Mar. 31, 2020	$ 11,747.8		$ 0.0	8,864.9	$ (2,213.0)	(101.5)	5,197.4
Balances, treasury shares at Mar. 31, 2020					17.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock, shares	2.3				2.3
Repurchase of common stock	$ (253.7)				$ (253.7)
Issuance of common stock under stock option and stock purchase plans, shares			0.1
Issuance of common stock under stock option and stock purchase plans	10.1			10.1
Issuance of restricted common stock, shares			0.2
Issuance of restricted common stock	0.0
Share-based compensation expense	64.1			67.4	$ (3.3)
Net (loss) income	(1,068.1)						(1,068.1)
Other comprehensive loss	$ (9.4)					(9.4)
Balances, treasury shares at Jun. 30, 2020	20.1				20.1
Balances, value at Jun. 30, 2020	$ 10,490.8		$ 0.0	$ 8,942.4	$ (2,470.0)	$ (110.9)	$ 4,129.3
Balances, common shares at Jun. 30, 2020			239.2