Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	$ 2,652.1		$ 2,652.1		$ 2,615.1
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates	137.4	$ 122.3	292.0	$ 238.0
Income Statement Data:
Revenues	497.9	461.3	1,014.4	857.3
Operating income	299.3	288.1	637.8	531.8
Net income	298.8	286.4	636.4	528.7
NGL Pipelines & Services [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	686.7		686.7		662.0
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates	26.7	39.4	56.8	58.8
Crude Oil Pipelines & Services [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	1,881.9		1,881.9		1,867.5
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates	111.0	83.5	235.6	181.4
Natural Gas Pipelines & Services [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	24.0		24.0		22.8
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates	1.6	1.6	3.3	2.6
Petrochemical & Refined Products Services [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	59.5		59.5		$ 62.8
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates	$ (1.9)	$ (2.2)	$ (3.7)	$ (4.8)