Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions		Common stock	Additional paid-in capital	Retained earnings (accumulated deficit)	Accumulated other comprehensive income (loss)	Treasury stock	Noncontrolling interest	Total
Balances at Dec. 31, 2017		$ 4.7	$ 9,925.2	$ 9,482.9	$ 165.5	$ (6,729.0)	$ 72.6	$ 12,921.9
Increase (decrease) in stockholders' equity
Common stock issued		0.1	44.5					44.6
Stock-based compensation			44.4	(3.6)			(0.5)	40.3
Treasury stock acquired, common						(396.5)		(396.5)
Dividends to common stockholders				(295.8)				(295.8)
Distributions to noncontrolling interest							(9.5)	(9.5)
Contributions from noncontrolling interest							2.0	2.0
Purchase of subsidiary shares from noncontrolling interest			(21.4)				(1.6)	(23.0)
Adjustments to redemption amount of redeemable noncontrolling interest			0.9				(0.3)	0.6
Effects of implementation of accounting change | ASU 2016-01 - Equity investments				1.0	(1.0)
Effects of implementation of accounting change | ASU 2014-09 - Revenue recognition				(65.0)	25.6		(0.3)	(39.7)
Effects of implementation of accounting change | ASU 2018-02 - Reclassification of certain tax effects				(77.6)	77.6
Effects of implementation of accounting change | ASU 2016-16 - Intra-entity asset transfer taxes				8.7				8.7
Net income (loss)				853.7			6.2	859.9
Other comprehensive income (loss)					(1,405.6)		(1.4)	(1,407.0)
Balances at Jun. 30, 2018		4.8	9,993.6	9,904.3	(1,137.9)	(7,125.5)	67.2	11,706.5
Balances at Mar. 31, 2018		4.7	9,981.8	9,598.3	(469.3)	(6,928.6)	68.9	12,255.8
Increase (decrease) in stockholders' equity
Common stock issued		0.1	12.0					12.1
Stock-based compensation			21.2	(2.1)			0.1	19.2
Treasury stock acquired, common						(196.9)		(196.9)
Dividends to common stockholders				(148.5)				(148.5)
Distributions to noncontrolling interest							(1.5)	(1.5)
Contributions from noncontrolling interest							1.9	1.9
Purchase of subsidiary shares from noncontrolling interest			(21.4)				(1.6)	(23.0)
Adjustments to redemption amount of redeemable noncontrolling interest							(0.3)	(0.3)
Net income (loss)	[1]			456.6			1.6	458.2
Other comprehensive income (loss)	[1]				(668.6)		(1.9)	(670.5)
Balances at Jun. 30, 2018		4.8	9,993.6	9,904.3	(1,137.9)	(7,125.5)	67.2	11,706.5
Balances at Dec. 31, 2018		4.8	10,060.7	10,290.2	(1,565.1)	(7,400.6)	66.0	11,456.0
Increase (decrease) in stockholders' equity
Common stock issued			22.1					22.1
Stock-based compensation			49.4	(4.0)			0.1	45.5
Treasury stock acquired, common						(153.7)		(153.7)
Dividends to common stockholders				(300.6)				(300.6)
Distributions to noncontrolling interest							(4.7)	(4.7)
Contributions from noncontrolling interest							1.8	1.8
Adjustments to redemption amount of redeemable noncontrolling interest			(1.5)				(0.2)	(1.7)
Effects of implementation of accounting change | ASU 2016-02 - Leases				4.0				4.0
Net income (loss)				816.2			3.7	819.9
Other comprehensive income (loss)					2,212.8		0.6	2,213.4
Balances at Jun. 30, 2019		4.8	10,130.7	10,805.8	647.7	(7,554.3)	67.3	14,102.0
Balances at Mar. 31, 2019		4.8	10,090.8	10,571.9	(418.9)	(7,554.2)	67.8	12,762.2
Increase (decrease) in stockholders' equity
Common stock issued			16.3					16.3
Stock-based compensation			22.6	(2.0)			0.1	20.7
Treasury stock acquired, common						(0.1)		(0.1)
Dividends to common stockholders				(150.4)				(150.4)
Distributions to noncontrolling interest							(3.4)	(3.4)
Contributions from noncontrolling interest							1.0	1.0
Adjustments to redemption amount of redeemable noncontrolling interest			1.0				(0.2)	0.8
Net income (loss)				386.3			1.8	388.1
Other comprehensive income (loss)					1,066.6		0.2	1,066.8
Balances at Jun. 30, 2019		$ 4.8	$ 10,130.7	$ 10,805.8	$ 647.7	$ (7,554.3)	$ 67.3	$ 14,102.0

[1] Excludes amounts attributable to redeemable noncontrolling interest. See Note 10, Stockholders’ Equity, for further details.