UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 10.6	$ 7.5
Intangible Assets, accumulated amortization	$ 1,169.7	$ 1,150.0
Limited partners:
Capital account, units outstanding (in units)	937,008,892	935,685,008