General Accounting Matters (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Income Tax Expense (Benefit) [Abstract]
Benefit from (provision for) income taxes	$ 34.4		$ (7.1)
Income tax benefit from the conversion of company structure	46.5
Other Nonoperating Income (Expense) [Abstract]
Gain on the sale of available-for sale securities	53.3	[1]	0	[1]
Distribution income from available-for-sale securities	4.1		0
Other	1.0		0.2
Other Nonoperating Income (Expense)	58.4		0.2
Allowance for Doubtful Accounts, Current [Member]
Activity of allowance for doubtful accounts [Roll Forward]
Balance at beginning of period	13.4		18.4
Charged to costs and expenses	0.1		0.2
Deductions	(0.5)	[2]	(5.1)	[2]
Balance at end of period	$ 13.0		$ 13.5

[1] Represents gains on the sale of Energy Transfer Equity common units. See Note 7 for information regarding our investment in Energy Transfer Equity.

[2] The 2011 deduction is primarily due to our reassessment of the allowance for doubtful accounts as a result of improved credit ratings of a significant customer, which reduced our exposure to potential uncollectibility.