Retrospective Adjustment - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities
Net income	$ 68.0	$ 49.1	[1],[2]
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, amortization and accretion	5.9	5.2	[1],[2]
Changes in operating assets and liabilities
Accounts receivable	0.3	11.2	[1]
Allowance oil	(0.4)	0.7	[1]
Prepaid expenses	1.6	1.4	[1]
Accounts payable	(0.2)	(6.6)	[1]
Deferred revenue	(1.8)	6.9	[1]
Accrued liabilities	(0.1)	4.7	[1]
Net cash provided by operating activities	72.4	72.6	[1]
Cash flows from investing activities
Capital expenditures	(4.7)	(2.6)	[1]
Return of investment	4.1	3.2	[1]
Payment of pre-IPO distributions from investments to SPLC	0.0	(11.9)	[1]
Net cash used in investing activities	(0.6)	(11.3)	[1]
Cash flows from financing activities
Distributions to noncontrolling interest	(12.4)	(25.1)	[1]
Distributions to unitholders and general partner	(35.3)	(14.4)	[1]
Net distribution to Parent	0.0	(15.1)	[1]
Net cash used in financing activities	(26.8)	(54.6)	[1]
Net increase in cash and cash equivalents	45.0	6.7	[1]
Cash and cash equivalents at beginning of the period	93.0	150.2	[1]
Cash and cash equivalents at end of the period	138.0	156.9	[1]
Change in accrued capital expenditures	$ 0.4	(0.5)	[1]
Pecten
Cash flows from operating activities
Net income		49.1
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, amortization and accretion		5.2
Changes in operating assets and liabilities
Accounts receivable		11.2
Allowance oil		0.7
Prepaid expenses		1.4
Accounts payable		(6.6)
Deferred revenue		6.9
Accrued liabilities		4.7
Net cash provided by operating activities		72.6
Cash flows from investing activities
Capital expenditures		(2.6)
Return of investment		3.2
Payment of pre-IPO distributions from investments to SPLC		(11.9)
Net cash used in investing activities		(11.3)
Cash flows from financing activities
Distributions to noncontrolling interest		(25.1)
Distributions to unitholders and general partner		(14.4)
Net distribution to Parent		(15.1)
Net cash used in financing activities		(54.6)
Net increase in cash and cash equivalents		6.7
Cash and cash equivalents at beginning of the period		150.2
Cash and cash equivalents at end of the period		156.9
Change in accrued capital expenditures		(0.5)
Shell Midstream Partners, L.P. | Pecten
Cash flows from operating activities
Net income		41.4
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, amortization and accretion		3.4
Changes in operating assets and liabilities
Accounts receivable		6.1
Allowance oil		0.3
Prepaid expenses		1.1
Accounts payable		(6.2)
Deferred revenue		6.9
Accrued liabilities		4.4
Net cash provided by operating activities		57.4
Cash flows from investing activities
Capital expenditures		(2.5)
Return of investment		3.2
Payment of pre-IPO distributions from investments to SPLC		(11.9)
Net cash used in investing activities		(11.2)
Cash flows from financing activities
Distributions to noncontrolling interest		(25.1)
Distributions to unitholders and general partner		(14.4)
Net distribution to Parent		0.0
Net cash used in financing activities		(39.5)
Net increase in cash and cash equivalents		6.7
Cash and cash equivalents at beginning of the period		150.2
Cash and cash equivalents at end of the period		156.9
Change in accrued capital expenditures		(0.5)
Shell Auger and Lockport Operations | Pecten
Cash flows from operating activities
Net income		7.7
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, amortization and accretion		1.8
Changes in operating assets and liabilities
Accounts receivable		5.1
Allowance oil		0.4
Prepaid expenses		0.3
Accounts payable		(0.4)
Deferred revenue		0.0
Accrued liabilities		0.3
Net cash provided by operating activities		15.2
Cash flows from investing activities
Capital expenditures		(0.1)
Return of investment		0.0
Payment of pre-IPO distributions from investments to SPLC		0.0
Net cash used in investing activities		(0.1)
Cash flows from financing activities
Distributions to noncontrolling interest		0.0
Distributions to unitholders and general partner		0.0
Net distribution to Parent		(15.1)
Net cash used in financing activities		(15.1)
Net increase in cash and cash equivalents		0.0
Cash and cash equivalents at beginning of the period		0.0
Cash and cash equivalents at end of the period		0.0
Change in accrued capital expenditures		$ 0.0

[1] (1) The 2015 financial information has been retrospectively adjusted for the acquisition of the Shell Auger and Lockport Operations.

[2] (1) The 2015 financial information has been retrospectively adjusted for the acquisition of the Shell Auger and Lockport Operations.