Revenues, Impact of Change in Accounting Policy (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017		Jun. 30, 2018		Jun. 30, 2017		Dec. 31, 2017
Assets [Abstract]
Accounts receivable - trade, net	$ 4,318.3				$ 4,318.3				$ 4,358.4
Prepaid and other current assets	446.1				446.1				312.7
Property, plant and equipment, net	37,054.5				37,054.5				35,620.4
Other assets	231.5				231.5				196.4
Liabilities and Equity
Other long-term liabilities	682.4				682.4				578.4
Partners' equity	22,671.6				22,671.6				$ 22,547.2
Condensed Consolidated Statement of Operations Information [Abstract]
Revenues	8,467.5	[1]	$ 6,607.6	[2]	17,766.0	[1]	$ 13,928.0	[2]
Costs and Expenses [Abstract]
Operating costs and expenses	7,552.0		5,730.2		15,774.7		12,063.4
Operating Activities [Abstract]
Net income	687.2		$ 666.0		1,598.7		1,437.0
Net effect of changes in operating accounts					(228.5)		82.1
Investing Activities [Abstract]
Contributions in aid of construction costs					0.0		$ 29.6
Balances Without Adoption [Member] | ASC 606 [Member]
Assets [Abstract]
Accounts receivable - trade, net	4,445.2				4,445.2
Prepaid and other current assets	319.2				319.2
Property, plant and equipment, net	37,028.3				37,028.3
Other assets	231.5				231.5
Liabilities and Equity
Other long-term liabilities	661.0				661.0
Partners' equity	22,666.8				22,666.8
Condensed Consolidated Statement of Operations Information [Abstract]
Revenues	8,304.1				17,485.6
Costs and Expenses [Abstract]
Operating costs and expenses	7,390.2				15,499.1
Operating Activities [Abstract]
Net income					1,593.9
Net effect of changes in operating accounts					(249.9)
Investing Activities [Abstract]
Contributions in aid of construction costs					26.2
Impact of Adoption [Member] | ASC 606 [Member]
Assets [Abstract]
Accounts receivable - trade, net	(126.9)				(126.9)
Prepaid and other current assets	126.9				126.9
Property, plant and equipment, net	26.2				26.2
Other assets	0.0				0.0
Liabilities and Equity
Other long-term liabilities	21.4				21.4
Partners' equity	4.8				4.8
Condensed Consolidated Statement of Operations Information [Abstract]
Revenues	163.4				280.4
Costs and Expenses [Abstract]
Operating costs and expenses	161.8				275.6
Operating Activities [Abstract]
Net income					4.8
Net effect of changes in operating accounts					21.4
Investing Activities [Abstract]
Contributions in aid of construction costs					(26.2)
Impact of Adoption [Member] | ASC 606 [Member] | Equity NGL Revenue [Member]
Condensed Consolidated Statement of Operations Information [Abstract]
Revenues	161.8				275.6
Impact of Adoption [Member] | ASC 606 [Member] | CIAC Revenue [Member]
Condensed Consolidated Statement of Operations Information [Abstract]
Revenues	$ 1.6				$ 4.8

[1] Revenues are accounted for under ASC 606 upon implementation at January 1, 2018.

[2] Revenues are accounted for under ASC 605 for historical periods prior to January 1, 2018.