Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Common Stock and Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance (in shares) at Dec. 31, 2017		365.5
Balance at Dec. 31, 2017	$ 4,680.9		$ 8,042.1	$ (5.4)	$ (3,355.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	374.7				374.7
Other comprehensive loss, net	(24.8)			(24.8)
Issuance of common stock (in shares)		9.1
Issuance of common stock	56.8		56.8
Repurchase and retirement of common stock (in shares)		(29.5)
Repurchase and retirement of common stock	(755.5)		(394.6)		(360.9)
Share-based compensation expense	181.1		181.1
Payments of cash dividends	(187.0)		(187.0)
Balance (in shares) at Sep. 30, 2018		345.1
Balance at Sep. 30, 2018	4,650.9		7,698.4	(24.5)	(3,023.0)
Balance (in shares) at Jun. 30, 2018		349.4
Balance at Jun. 30, 2018	4,417.7		7,609.8	(16.4)	(3,175.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	223.8				223.8
Other comprehensive loss, net	(8.1)			(8.1)
Issuance of common stock (in shares)		1.7
Issuance of common stock	27.3		27.3
Repurchase and retirement of common stock (in shares)		(6.0)
Repurchase and retirement of common stock	(151.3)		(80.2)		(71.1)
Purchase of forward contract under accelerated share repurchase program (ASR)	150.0
Share-based compensation expense	53.6		53.6
Payments of cash dividends	(62.1)		(62.1)
Balance (in shares) at Sep. 30, 2018		345.1
Balance at Sep. 30, 2018	4,650.9		7,698.4	(24.5)	(3,023.0)
Balance (in shares) at Dec. 31, 2018		346.4
Balance at Dec. 31, 2018	4,823.2		7,672.8	(18.2)	(2,831.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	176.6				176.6
Other comprehensive loss, net	(8.6)			(8.6)
Issuance of common stock (in shares)		8.5
Issuance of common stock	55.4		55.4
Repurchase and retirement of common stock (in shares)		(13.9)
Repurchase and retirement of common stock	(354.9)		(181.7)		(173.2)
Common stock assumed upon business combination	4.7		4.7
Share-based compensation expense	147.1		147.1
Payments of cash dividends	(196.4)		(196.4)
Balance (in shares) at Sep. 30, 2019		341.0
Balance at Sep. 30, 2019	4,642.4		7,501.9	(26.8)	(2,832.7)
Balance (in shares) at Jun. 30, 2019		344.5
Balance at Jun. 30, 2019	4,591.2		7,491.2	(11.3)	(2,888.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	99.3				99.3
Other comprehensive loss, net	(15.5)			(15.5)
Issuance of common stock (in shares)		1.7
Issuance of common stock	25.7		25.7
Repurchase and retirement of common stock (in shares)		(5.2)
Repurchase and retirement of common stock	(111.1)		(67.8)		(43.3)
Purchase of forward contract under accelerated share repurchase program (ASR)	60.0		60.0
Share-based compensation expense	57.5		57.5
Payments of cash dividends	(64.7)		(64.7)
Balance (in shares) at Sep. 30, 2019		341.0
Balance at Sep. 30, 2019	$ 4,642.4		$ 7,501.9	$ (26.8)	$ (2,832.7)