Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 54.9	$ 43.2
Preferred stock rate	5.00%	5.00%
Preferred stock authorized (in dollars per shares)	$ 0.01	$ 0.01
Preferred stock authorized (in shares)	15,000,000	15,000,000
Preferred stock issued (in shares)	1,400,000	0
Preferred stock outstanding (in shares)	1,400,000	0
Common stock authorized (in dollars per shares)	$ 0.01	$ 0.01
Common stock authorized (in shares)	2,000,000,000	2,000,000,000
Common stock issued (in shares)	335,100,000	348,200,000
Common stock outstanding (in shares)	334,500,000	347,800,000