Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, net of allowances	$ 6.2	$ 8.4
Preferred stock authorized (in shares)	1,000,000,000	1,000,000,000
Preferred stock issued (in shares)	0	0
Common stock authorized (in shares)	5,000,000,000	5,000,000,000
Common stock issued (in shares)	373,011,513	365,643,911
Common stock outstanding (in shares)	373,011,513	365,643,911