Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Shares	Common Stock and Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning balance (shares) at Dec. 31, 2017			365,500,000
Stockholders' equity, beginning balance at Dec. 31, 2017	$ 4,680.9			$ 8,042.1	$ (5.4)	$ (3,355.8)
Stockholders' equity, beginning balance (Accounting Standards Update 2014-09) at Dec. 31, 2017		$ 324.7					$ 324.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	566.9					566.9
Other comprehensive income (loss), net of tax	(18.5)				(18.5)
Issuance of common stock (in shares)			10,400,000
Issuance of common stock	56.9			56.9
Repurchase and retirement of common stock (in shares)			(29,500,000)
Repurchase and retirement of common stock	(756.6)			(395.1)		(361.5)
Share-based compensation expense	218.2			218.2
Payment of cash dividends	(249.3)			(249.3)
Reclassification of tax effects upon adoption of ASU 2018-02 ("Topic 220"), net	0.0				5.7	(5.7)
Ending balance (shares) at Dec. 31, 2018			346,400,000
Stockholders' equity, ending balance at Dec. 31, 2018	4,823.2			7,672.8	(18.2)	(2,831.4)
Stockholders' equity, ending balance (Accounting Standards Update 2017-12) at Dec. 31, 2018		0.1					0.1
Stockholders' equity, ending balance (Accounting Standards Update 2016-02) at Dec. 31, 2018		$ (4.8)					$ (4.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	345.0					345.0
Other comprehensive income (loss), net of tax	(0.3)				(0.3)
Issuance of common stock (in shares)			9,800,000
Issuance of common stock	55.6			55.6
Common stock assumed upon business combination	4.6			4.6
Repurchase and retirement of common stock (in shares)			(20,300,000)
Repurchase and retirement of common stock	(514.9)			(264.6)		(250.3)
Purchase of forward contract under accelerated share repurchase program ("ASR")	(40.0)			(40.0)
Share-based compensation expense	202.2			202.2
Payment of cash dividends	$ (260.1)			(260.1)
Ending balance (shares) at Dec. 31, 2019	335,900,000		335,900,000
Stockholders' equity, ending balance at Dec. 31, 2019	$ 4,610.6			7,370.5	(18.5)	(2,741.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	257.8					257.8
Other comprehensive income (loss), net of tax	74.1				74.1
Issuance of common stock (in shares)			10,000,000.0
Issuance of common stock	54.7			54.7
Common stock assumed upon business combination	1.5			1.5
Repurchase and retirement of common stock (in shares)			(18,200,000)
Repurchase and retirement of common stock	(421.1)			(235.7)		(185.4)
Purchase of forward contract under accelerated share repurchase program ("ASR")	40.0			40.0
Share-based compensation expense	190.0			190.0
Payment of cash dividends	$ (264.1)			(264.1)
Ending balance (shares) at Dec. 31, 2020	327,700,000		327,700,000
Stockholders' equity, ending balance at Dec. 31, 2020	$ 4,543.5			$ 7,156.9	$ 55.6	$ (2,669.0)