CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Accounts receivable, allowance for doubtful accounts	$ 11.3	$ 12.1
Intangible assets, accumulated amortization	$ 1,403.1	$ 1,235.8
Limited partners:
Common units outstanding (in units)	2,117,588,414	2,012,553,024