Equity - Schedule of Stock by Class (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Class A
Class of Stock [Line Items]
Common stock outstanding (in shares)	143.2	162.4	142.4	77.3
Stock Issued During Period, Shares, New Issues	0.7	0.6	0.7
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited	(0.1)	0.0	0.0
Stock Repurchased During Period, Shares	(19.8)	(2.6)	0.0
Stock Issued During Period, Shares, Conversion of Convertible Securities	0.0	(22.0)	(64.4)
Common Class B
Class of Stock [Line Items]
Common stock outstanding (in shares)	25.4	25.4	47.4	111.8
Stock Issued During Period, Shares, Conversion of Convertible Securities	0.0	(22.0)	(64.4)
Common Class M-1
Class of Stock [Line Items]
Common stock outstanding (in shares)	3.3	3.4	3.4	3.5
Stock Issued During Period, Shares, Conversion of Convertible Securities	(0.1)	0.0	(0.1)
Common Class M-2
Class of Stock [Line Items]
Common stock outstanding (in shares)	0.8	0.8	0.9	1.1
Stock Issued During Period, Shares, Conversion of Convertible Securities	0.0	(0.1)	(0.2)
Common Class M-3
Class of Stock [Line Items]
Common stock outstanding (in shares)	1.0	1.0	1.1	1.3
Stock Issued During Period, Shares, Conversion of Convertible Securities	0.0	(0.1)	(0.2)
Common Class M-4
Class of Stock [Line Items]
Common stock outstanding (in shares)	4.0	4.1	4.7	5.4
Stock Repurchased During Period, Shares	0.0	(0.1)	(0.4)
Stock Issued During Period, Shares, Conversion of Convertible Securities	0.1	0.5	0.2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	0.0	0.0	(0.1)