CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
ASSETS
Accounts receivable, allowance for doubtful accounts	$ 12.4	$ 11.5
Intangible assets, accumulated amortization	$ 1,687.5	$ 1,735.1
Limited partners:
Common units outstanding (in units)	2,189,226,130	2,184,869,029