CONSOLIDATED CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Total Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2018		215.2	7.5
Beginning balance at Dec. 31, 2018	$ 3,140.4	$ 215.2	$ (1,015.4)	$ 1,384.4	$ 2,694.7	$ (138.5)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	249.7				249.7
Other comprehensive income (loss), net of tax	(2.7)					(2.7)
Common stock issued under equity plans (in shares)		0.8
Common stock issued under equity plans	45.0	$ 0.8		44.2
Stock-based compensation expense	20.8			20.8
Purchases of treasury stock (in shares)			0.1
Purchases of treasury stock	(5.7)		$ (5.7)
Ending balance (in shares) at Mar. 31, 2019		216.0	7.6
Ending balance at Mar. 31, 2019	3,447.5	$ 216.0	$ (1,021.1)	1,449.4	2,944.4	(141.2)
Beginning balance (in shares) at Dec. 31, 2018		215.2	7.5
Beginning balance at Dec. 31, 2018	3,140.4	$ 215.2	$ (1,015.4)	1,384.4	2,694.7	(138.5)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	766.7
Other comprehensive income (loss), net of tax	(17.3)
Ending balance (in shares) at Sep. 30, 2019		217.5	9.0
Ending balance at Sep. 30, 2019	3,814.8	$ 217.5	$ (1,278.7)	1,570.4	3,461.4	(155.8)
Beginning balance (in shares) at Mar. 31, 2019		216.0	7.6
Beginning balance at Mar. 31, 2019	3,447.5	$ 216.0	$ (1,021.1)	1,449.4	2,944.4	(141.2)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	242.3				242.3
Other comprehensive income (loss), net of tax	3.0					3.0
Common stock issued under equity plans (in shares)		0.9
Common stock issued under equity plans	41.5	$ 0.9		40.6
Stock-based compensation expense	22.3			22.3
Purchases of treasury stock (in shares)			1.4
Purchases of treasury stock	(256.3)		$ (256.3)
Ending balance (in shares) at Jun. 30, 2019		216.9	9.0
Ending balance at Jun. 30, 2019	3,500.3	$ 216.9	$ (1,277.4)	1,512.3	3,186.7	(138.2)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	274.7				274.7
Other comprehensive income (loss), net of tax	(17.6)					(17.6)
Common stock issued under equity plans (in shares)		0.6
Common stock issued under equity plans	38.9	$ 0.6		38.3
Stock-based compensation expense	19.8			19.8
Purchases of treasury stock	(1.3)		$ (1.3)
Ending balance (in shares) at Sep. 30, 2019		217.5	9.0
Ending balance at Sep. 30, 2019	3,814.8	$ 217.5	$ (1,278.7)	1,570.4	3,461.4	(155.8)
Beginning balance (in shares) at Dec. 31, 2019		218.1	9.0
Beginning balance at Dec. 31, 2019	4,148.3	$ 218.1	$ (1,278.7)	1,623.3	3,741.6	(156.0)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	310.6				310.6
Other comprehensive income (loss), net of tax	4.0					4.0
Common stock issued under equity plans (in shares)		0.4
Common stock issued under equity plans	29.1	$ 0.4		28.7
Stock-based compensation expense	23.9			23.9
Purchases of treasury stock (in shares)			3.0
Purchases of treasury stock	(614.8)		$ (614.8)
Ending balance (in shares) at Mar. 31, 2020		218.5	12.0
Ending balance at Mar. 31, 2020	3,901.1	$ 218.5	$ (1,893.5)	1,675.9	4,052.2	(152.0)
Beginning balance (in shares) at Dec. 31, 2019		218.1	9.0
Beginning balance at Dec. 31, 2019	4,148.3	$ 218.1	$ (1,278.7)	1,623.3	3,741.6	(156.0)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	513.9
Other comprehensive income (loss), net of tax	(1.9)
Ending balance (in shares) at Sep. 30, 2020		635.0	12.1
Ending balance at Sep. 30, 2020	4,210.3	$ 635.0	$ (1,903.9)	1,381.6	4,255.5	(157.9)
Beginning balance (in shares) at Mar. 31, 2020		218.5	12.0
Beginning balance at Mar. 31, 2020	3,901.1	$ 218.5	$ (1,893.5)	1,675.9	4,052.2	(152.0)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(121.9)				(121.9)
Other comprehensive income (loss), net of tax	5.9					5.9
Common stock issued under equity plans (in shares)		1.2
Common stock issued under equity plans	38.2	$ 1.2		37.0
Stock-based compensation expense	24.8			24.8
Purchases of treasury stock (in shares)			0.1
Purchases of treasury stock	(9.0)		$ (9.0)
Stock issued to effect stock split (in shares)		413.8
Stock issued to effect stock split (Note 1)	0.0	$ 413.8		(413.8)
Ending balance (in shares) at Jun. 30, 2020		633.5	12.1
Ending balance at Jun. 30, 2020	3,839.1	$ 633.5	$ (1,902.5)	1,323.9	3,930.3	(146.1)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	325.2				325.2
Other comprehensive income (loss), net of tax	(11.8)					(11.8)
Common stock issued under equity plans (in shares)		1.5
Common stock issued under equity plans	36.2	$ 1.5		34.7
Stock-based compensation expense	23.0			23.0
Purchases of treasury stock	(1.4)		$ (1.4)
Ending balance (in shares) at Sep. 30, 2020		635.0	12.1
Ending balance at Sep. 30, 2020	$ 4,210.3	$ 635.0	$ (1,903.9)	$ 1,381.6	$ 4,255.5	$ (157.9)