CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - USD ($) $ in Millions	Total	Common stock issued, Class A	Common stock issued, Class B	Exchangeable shares issued, Class A	Exchangeable shares issued, Class B	Retained earnings	Accumulated other comprehensive income (loss)	Common stock held in treasury, Class B	Paid-in capital	Noncontrolling interest
Balance at Dec. 31, 2013	$ 8,630.1	$ 0.0	$ 1.7	$ 108.5	$ 714.1	$ 4,199.5	$ 154.9	$ (321.1)	$ 3,747.6	$ 24.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exchange of shares	0.0			0.0	(52.6)				52.6
Shares issued under equity compensation plan	47.9		0.0						47.9
Amortization of share-based compensation	21.7								21.7
Purchase of noncontrolling interest	(0.4)								1.4	(1.8)
Net income (loss) including noncontrolling interests	517.8					514.0				3.8
Other comprehensive income (loss), net of tax	(1,053.3)						(1,053.3)
Dividends declared and paid	(277.7)					(273.6)				(4.1)
Balance at Dec. 31, 2014	7,886.1	0.0	1.7	108.5	661.5	4,439.9	(898.4)	(321.1)	3,871.2	22.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exchange of shares	0.0			(0.3)	(58.5)				58.8
Shares issued under equity compensation plan	48.9								48.9
Amortization of share-based compensation	21.2								21.2
Purchase of noncontrolling interest	(0.3)								0.3	(0.6)
Net income (loss) including noncontrolling interests	362.8					359.5				3.3
Other comprehensive income (loss), net of tax	(797.5)						(796.5)			(1.0)
Repurchase of common stock	(150.3)		(150.0)					(150.3)
Dividends declared and paid	(307.8)					(303.4)				(4.4)
Balance at Dec. 31, 2015	7,063.1	0.0	1.7	108.2	603.0	4,496.0	(1,694.9)	(471.4)	4,000.4	20.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exchange of shares	0.0			(0.1)	(31.8)				31.9
Shares issued under equity compensation plan	(1.1)								(1.1)
Amortization of share-based compensation	32.3								32.3
Replacement share-based awards issued in conjunction with Acquisition	46.4								46.4
Acquisition of businesses	186.3									186.3
Purchase of noncontrolling interest	(0.1)								0.1	(0.2)
Net income (loss) including noncontrolling interests	1,981.8					1,975.9				5.9
Other comprehensive income (loss), net of tax	146.5						149.4			(2.9)
Stock Issued During Period, Value, New Issues	2,525.6		0.3						2,525.3
Dividends declared and paid	(359.1)					(352.9)				(6.2)
Balance at Dec. 31, 2016	$ 11,621.7	$ 0.0	$ 2.0	$ 108.1	$ 571.2	$ 6,119.0	$ (1,545.5)	$ (471.4)	$ 6,635.3	$ 203.0