CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - USD ($) $ in Millions	Total	Class A common stock, voting [Member]	Common Class B [Member]	Exchangeable shares issued, Class A	Exchangeable shares issued, Class B	Retained earnings	AOCI Attributable to Parent [Member]	Common stock held in treasury, Class B	Paid-in capital	Noncontrolling interest
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			0.0	(21.6)				21.6
Shares issued under equity compensation plan	(7.9)								(7.9)
Amortization of share-based compensation	6.7								6.7
Net income (loss) including noncontrolling interests	163.5					162.7				0.8
Other comprehensive income (loss), net of tax	256.6						257.0			(0.4)
Stock Issued During Period, Value, New Issues	2,525.6		0.3						2,525.3
Dividends declared and paid	(88.3)					(88.3)
Balance at Mar. 31, 2016	9,919.3	0.0	2.0	108.2	581.4	4,570.4	(1,437.9)	(471.4)	6,546.1	20.5
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exchange of shares	0.0			0.3	(3.6)				3.3
Shares issued under equity compensation plan	23.5								23.5
Amortization of share-based compensation	14.8								14.8
Acquisition of business and purchase of noncontrolling interest	2.1									2.1
Net income (loss) including noncontrolling interests	207.8					201.3				6.5
Other comprehensive income (loss), net of tax	75.7						75.3			0.4
Dividends declared and paid	(88.3)					(88.3)
Balance at Mar. 31, 2017	$ 11,810.3	$ 0.0	$ 2.0	$ 108.4	$ 567.6	$ 6,232.0	$ (1,470.2)	$ (471.4)	$ 6,629.9	$ 212.0