General Accounting Matters (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended					9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Mar. 31, 2012	Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Income Tax Expense (Benefit) [Abstract]
Provision for (benefit from) income taxes	$ 19.4		$ 2.4			$ 46.2		$ (23.5)
Income tax expense due to changes in Texas Margin Tax						19.6
Income tax benefit from the conversion of company structure					46.5
Deferred Income Tax Expense (Benefit)						32.1		(67.9)
Current Income Tax Expense						14.1
Cash payments for income taxes								22.0
Other Nonoperating Income (Expense) [Abstract]
Gain on sales of available-for-sale securities of Energy Transfer Equity	0	[1]	0	[1]		0	[1]	68.8	[1]
Distribution income from Energy Transfer Equity	0		0			0		4.1
Other	0.4		1.2			(0.5)		(0.2)
Total	0.4		1.2			(0.5)		72.7
Restricted cash [Abstract]
Restricted cash	35.9					35.9				4.3
Allowance for Doubtful Accounts, Current [Member]
Movement in valuation allowances and reserves [Roll Forward]
Balance at beginning of period					13.4	13.2		13.4
Charged to costs and expenses						1.2		0.2
Deductions						(7.7)		(0.4)
Balance at end of period	$ 6.7		$ 13.2			$ 6.7		$ 13.2

[1] See Note 7 for information regarding the liquidation of our investment in limited partnership units of Energy Transfer Equity.