Acquisitions and Divestiture - Balance Sheet (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Current assets
Cash and cash equivalents		$ 137.7	$ 122.1	[1],[2]	$ 93.8	[2]	$ 150.2	[2]
Accounts receivable - third parties, net		17.2	22.7	[1]
Accounts receivable - related parties		23.8	19.3	[1]
Allowance oil		12.4	11.7	[1]
Prepaid expenses		12.5	6.7	[1]
Total current assets		203.6	182.5	[1]
Equity method investments		362.6	324.7	[1]
Property, plant and equipment, net		736.5	733.7	[1]
Cost investments		62.1	62.1	[1]
Other assets		1.7	0.9	[1]
Total assets		1,366.5	1,303.9	[1]
Current liabilities
Accounts payable - third parties		4.0	7.2	[1]
Accounts payable - related parties		11.6	5.6	[1]
Deferred revenue - third parties		5.5	6.0	[1]
Deferred revenue - related parties		13.9	7.9	[1]
Accrued liabilities - third parties		12.7	12.2	[1]
Accrued liabilities - related parties		7.2	5.1	[1]
Total current liabilities		54.9	44.0	[1]
Noncurrent liabilities
Debt payable - related party		1,844.0	686.0	[1]
Lease liability (4)		24.3	24.9	[1]
Accrued liabilities - third party		0.0	6.3	[1]
Asset retirement obligations		6.6	6.4	[1]
Other unearned income		2.6	2.1	[1]
Total noncurrent liabilities		1,877.5	725.7	[1]
Total liabilities		1,932.4	769.7	[1]
Commitments and Contingencies (Note 13)				[1]
Equity [Abstract]
Total partners' (deficit) capital		(589.2)	98.3	[1]
Noncontrolling interest		23.3	21.5	[1]
Net parent investment		0.0	414.4	[1]
Total (deficit) equity	[3]	(565.9)	534.2	[1]	632.5		1,088.7
Total liabilities and (deficit) equity		1,366.5	1,303.9	[1]
Scenario, Previously Reported
Current assets
Cash and cash equivalents			121.9		93.0		150.2
Accounts receivable - third parties, net			18.4
Accounts receivable - related parties			10.1
Allowance oil			9.0
Prepaid expenses			6.0
Total current assets			165.4
Equity method investments			262.4
Property, plant and equipment, net			398.0
Cost investments			39.8
Other assets			0.0
Total assets			865.6
Current liabilities
Accounts payable - third parties			1.5
Accounts payable - related parties			5.2
Deferred revenue - third parties			6.0
Deferred revenue - related parties			7.9
Accrued liabilities - third parties			5.6
Accrued liabilities - related parties			5.1
Total current liabilities			31.3
Noncurrent liabilities
Debt payable - related party			686.0
Lease liability (4)			24.9
Accrued liabilities - third party			0.0
Asset retirement obligations			1.4
Other unearned income			2.1
Total noncurrent liabilities			714.4
Total liabilities			745.7
Commitments and Contingencies (Note 13)
Equity [Abstract]
Total partners' (deficit) capital			98.3
Noncontrolling interest			21.6
Net parent investment			0.0
Total (deficit) equity			119.9
Total liabilities and (deficit) equity			865.6
General Public | Common Units
Equity [Abstract]
Common and subordinated unitholders		2,773.5	2,485.7	[1]
General Public | Common Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			2,485.7
Shell Pipeline Company L P
Equity [Abstract]
General partner – SPLC		(2,855.5)	(1,873.7)	[1]
Shell Pipeline Company L P | Scenario, Previously Reported
Equity [Abstract]
General partner – SPLC			(1,873.7)
Shell Pipeline Company L P | Common Units
Equity [Abstract]
Common and subordinated unitholders		(507.2)	(124.1)	[1]
Shell Pipeline Company L P | Common Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			(124.1)
Shell Pipeline Company L P | Subordinated Units
Equity [Abstract]
Common and subordinated unitholders		0.0	(389.6)	[1]
Total (deficit) equity		$ 0.0	(389.6)		(409.8)		(440.9)
Shell Pipeline Company L P | Subordinated Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			(389.6)
May 2017 Acquisition | Scenario, Previously Reported
Current assets
Cash and cash equivalents			0.0		0.0		0.0
Accounts receivable - third parties, net			2.4
Accounts receivable - related parties			2.0
Allowance oil			2.7
Prepaid expenses			0.5
Total current assets			7.6
Equity method investments			0.0
Property, plant and equipment, net			212.6
Cost investments			0.0
Other assets			0.6
Total assets			220.8
Current liabilities
Accounts payable - third parties			2.6
Accounts payable - related parties			0.2
Deferred revenue - third parties			0.0
Deferred revenue - related parties			0.0
Accrued liabilities - third parties			1.3
Accrued liabilities - related parties			0.0
Total current liabilities			4.1
Noncurrent liabilities
Debt payable - related party			0.0
Lease liability (4)			0.0
Accrued liabilities - third party			0.0
Asset retirement obligations			0.0
Other unearned income			0.0
Total noncurrent liabilities			0.0
Total liabilities			4.1
Commitments and Contingencies (Note 13)
Equity [Abstract]
Total partners' (deficit) capital			0.0
Noncontrolling interest			0.0
Net parent investment			216.7
Total (deficit) equity			216.7
Total liabilities and (deficit) equity			220.8
May 2017 Acquisition | General Public | Common Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			0.0
May 2017 Acquisition | Shell Pipeline Company L P | Scenario, Previously Reported
Equity [Abstract]
General partner – SPLC			0.0
May 2017 Acquisition | Shell Pipeline Company L P | Common Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			0.0
May 2017 Acquisition | Shell Pipeline Company L P | Subordinated Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			0.0
December 2017 Acquisition | Scenario, Previously Reported
Current assets
Cash and cash equivalents			0.2		$ 0.8		$ 0.0
Accounts receivable - third parties, net			1.9
Accounts receivable - related parties			7.2
Allowance oil			0.0
Prepaid expenses			0.2
Total current assets			9.5
Equity method investments			62.3
Property, plant and equipment, net			123.1
Cost investments			22.3
Other assets			0.3
Total assets			217.5
Current liabilities
Accounts payable - third parties			3.1
Accounts payable - related parties			0.2
Deferred revenue - third parties			0.0
Deferred revenue - related parties			0.0
Accrued liabilities - third parties			5.3
Accrued liabilities - related parties			0.0
Total current liabilities			8.6
Noncurrent liabilities
Debt payable - related party			0.0
Lease liability (4)			0.0
Accrued liabilities - third party			6.3
Asset retirement obligations			5.0
Other unearned income			0.0
Total noncurrent liabilities			11.3
Total liabilities			19.9
Commitments and Contingencies (Note 13)
Equity [Abstract]
Total partners' (deficit) capital			0.0
Noncontrolling interest			(0.1)
Net parent investment			197.7
Total (deficit) equity			197.6
Total liabilities and (deficit) equity			217.5
December 2017 Acquisition | General Public | Common Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			0.0
December 2017 Acquisition | Shell Pipeline Company L P | Scenario, Previously Reported
Equity [Abstract]
General partner – SPLC			0.0
December 2017 Acquisition | Shell Pipeline Company L P | Common Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			0.0
December 2017 Acquisition | Shell Pipeline Company L P | Subordinated Units | Scenario, Previously Reported
Equity [Abstract]
Common and subordinated unitholders			$ 0.0

[1] The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

[2] The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

[3] The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.