CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common Stock and Additional Paid-in-Capital	Common Stock Held in Treasury	Accumulated Other Comprehensive Loss	Retained Earnings
Balance, common stock shares issued (in shares) at Mar. 31, 2020		516,800,000
Beginning balance at Mar. 31, 2020	$ 5,585.5	$ 2,675.3	$ (500.6)	$ (21.6)	$ 3,432.4
Balance, common stock held in treasury (in shares) at Mar. 31, 2020			26,100,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	123.6				123.6
Other comprehensive income	0.5			0.5
Proceeds from sales of common stock through employee equity incentive plans (shares)		1,200,000
Proceeds from sales of common stock through employee equity incentive plans	11.0	$ 11.0
RSU and SAR withholdings (shares)		(300,000)
RSU and SAR withholdings	(11.0)	$ (11.0)
Treasury stock used for new issuances (shares)		(900,000)	(900,000)
Treasury stock used for new issuances	0.0	$ (14.8)	$ 14.8
Shares issued to settle convertible debt (in shares)		13,300,000
Value of Shares Issued	651.5	$ 651.5
Settlement of convertible debt	(810.7)	(810.7)
Share-based compensation	41.3	$ 41.3
Cash dividend	(90.4)				(90.4)
Balance, common stock shares issued (in shares) at Jun. 30, 2020		530,100,000
Ending balance at Jun. 30, 2020	5,501.3	$ 2,542.6	$ (485.8)	(21.1)	3,465.6
Balance, common stock held in treasury (in shares) at Jun. 30, 2020			25,200,000
Balance, common stock shares issued (in shares) at Mar. 31, 2020		516,800,000
Beginning balance at Mar. 31, 2020	5,585.5	$ 2,675.3	$ (500.6)	(21.6)	3,432.4
Balance, common stock held in treasury (in shares) at Mar. 31, 2020			26,100,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	197.2
Other comprehensive income	0.7
Balance, common stock shares issued (in shares) at Sep. 30, 2020		544,500,000
Ending balance at Sep. 30, 2020	5,443.7	$ 2,487.7	$ (467.0)	(20.9)	3,443.9
Balance, common stock held in treasury (in shares) at Sep. 30, 2020			24,000,000.0
Balance, common stock shares issued (in shares) at Jun. 30, 2020		530,100,000
Beginning balance at Jun. 30, 2020	5,501.3	$ 2,542.6	$ (485.8)	(21.1)	3,465.6
Balance, common stock held in treasury (in shares) at Jun. 30, 2020			25,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	73.6				73.6
Other comprehensive income	0.2			0.2
Proceeds from sales of common stock through employee equity incentive plans (shares)		1,500,000
Proceeds from sales of common stock through employee equity incentive plans	18.6	$ 18.6
RSU and SAR withholdings (shares)		(300,000)
RSU and SAR withholdings	(14.4)	$ (14.4)
Treasury stock used for new issuances (shares)		(1,200,000)	(1,200,000)
Treasury stock used for new issuances	0.0	$ (18.8)	$ 18.8
Shares issued to settle convertible debt (in shares)		14,400,000
Value of Shares Issued	768.7	$ 768.7
Settlement of convertible debt	(859.4)	(859.4)
Share-based compensation	50.4	$ 50.4
Cash dividend	(95.3)				(95.3)
Balance, common stock shares issued (in shares) at Sep. 30, 2020		544,500,000
Ending balance at Sep. 30, 2020	$ 5,443.7	$ 2,487.7	$ (467.0)	(20.9)	3,443.9
Balance, common stock held in treasury (in shares) at Sep. 30, 2020			24,000,000.0
Balance, common stock shares issued (in shares) at Mar. 31, 2021	568,958,158	569,000,000.0
Beginning balance at Mar. 31, 2021	$ 5,337.1	$ 2,403.6	$ (433.8)	(26.2)	3,393.5
Balance, common stock held in treasury (in shares) at Mar. 31, 2021	21,900,970		21,900,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 252.8				252.8
Other comprehensive income	0.0			0.0
Proceeds from sales of common stock through employee equity incentive plans (shares)		1,400,000
Proceeds from sales of common stock through employee equity incentive plans	12.2	$ 12.2
RSU and SAR withholdings (shares)		(400,000)
RSU and SAR withholdings	(25.3)	$ (25.3)
Treasury stock used for new issuances (shares)		(1,000,000.0)	(1,000,000.0)
Treasury stock used for new issuances	0.0	$ (16.3)	$ 16.3
Share-based compensation	56.2	$ 56.2
Cash dividend	(113.1)				(113.1)
Balance, common stock shares issued (in shares) at Jun. 30, 2021		569,000,000.0
Ending balance at Jun. 30, 2021	$ 5,519.9	$ 2,430.4	$ (417.5)	(26.2)	3,533.2
Balance, common stock held in treasury (in shares) at Jun. 30, 2021			20,900,000
Balance, common stock shares issued (in shares) at Mar. 31, 2021	568,958,158	569,000,000.0
Beginning balance at Mar. 31, 2021	$ 5,337.1	$ 2,403.6	$ (433.8)	(26.2)	3,393.5
Balance, common stock held in treasury (in shares) at Mar. 31, 2021	21,900,970		21,900,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 494.8
Other comprehensive income	$ 1.8			1.8
Balance, common stock shares issued (in shares) at Sep. 30, 2021	574,437,650	574,400,000
Ending balance at Sep. 30, 2021	$ 5,702.9	$ 2,471.2	$ (397.9)	(24.4)	3,654.0
Balance, common stock held in treasury (in shares) at Sep. 30, 2021	19,567,720		19,600,000
Balance, common stock shares issued (in shares) at Jun. 30, 2021		569,000,000.0
Beginning balance at Jun. 30, 2021	$ 5,519.9	$ 2,430.4	$ (417.5)	(26.2)	3,533.2
Balance, common stock held in treasury (in shares) at Jun. 30, 2021			20,900,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	242.0				242.0
Other comprehensive income	1.8			1.8
Proceeds from sales of common stock through employee equity incentive plans (shares)		1,600,000
Proceeds from sales of common stock through employee equity incentive plans	21.2	$ 21.2
RSU and SAR withholdings (shares)		(300,000)
RSU and SAR withholdings	(23.8)	$ (23.8)
Treasury stock used for new issuances (shares)		(1,300,000)	(1,300,000)
Treasury stock used for new issuances	0.0	$ (19.6)	$ 19.6
Shares issued to settle convertible debt (in shares)		5,400,000
Value of Shares Issued	399.2	$ 399.2
Settlement of convertible debt	(391.1)	(391.1)
Share-based compensation	54.9	$ 54.9
Cash dividend	$ (121.2)				(121.2)
Balance, common stock shares issued (in shares) at Sep. 30, 2021	574,437,650	574,400,000
Ending balance at Sep. 30, 2021	$ 5,702.9	$ 2,471.2	$ (397.9)	$ (24.4)	$ 3,654.0
Balance, common stock held in treasury (in shares) at Sep. 30, 2021	19,567,720		19,600,000