Guarantee of Securities of Subsidiaries Guarantee of Securities of Subsidiaries Statements of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Statement of Cash Flows
Net cash provided by (used in) operating activities	$ 454.2	$ 430.2
Investing Activities:
Capital expenditures	(432.4)	(241.1)
Proceeds from sale of operating assets	0.2	0.3
Proceeds from other recoveries	0.0	6.2
Advances to affiliates, net	0.0	0.0
Net cash provided by (used in) investing activities	(432.2)	(234.6)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	539.1	247.1
Repayment of borrowings from long-term debt and term loan	0.0	(725.0)
Proceeds from borrowings on revolving credit agreement	255.0	980.0
Repayment of borrowings on revolving credit agreement, including financing fees	(630.8)	(738.6)
Principal payment of capital lease obligation	(0.3)	(0.3)
Advances from affiliates, net	0.0	0.6
Distributions paid	(76.7)	(76.0)
Proceeds from sale of common units	0.0	113.1
Capital contributions from general partner	0.0	2.3
Net cash (used in) provided by financing activities	86.3	(196.8)
Increase (decrease) in cash and cash equivalents	108.3	(1.2)
Cash and cash equivalents at beginning of period	3.1	6.6
Cash and cash equivalents at end of period	111.4	5.4
Reportable Legal Entities | Parent Guarantor
Statement of Cash Flows
Net cash provided by (used in) operating activities	27.3	20.4
Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from sale of operating assets	0.0	0.0
Proceeds from other recoveries		0.0
Advances to affiliates, net	49.7	(60.9)
Net cash provided by (used in) investing activities	49.7	(60.9)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0.0	0.0
Repayment of borrowings from long-term debt and term loan		0.0
Proceeds from borrowings on revolving credit agreement	0.0	0.0
Repayment of borrowings on revolving credit agreement, including financing fees	0.0	0.0
Principal payment of capital lease obligation	0.0	0.0
Advances from affiliates, net	0.0	0.6
Distributions paid	(76.7)	(76.0)
Proceeds from sale of common units		113.1
Capital contributions from general partner		2.3
Net cash (used in) provided by financing activities	(76.7)	40.0
Increase (decrease) in cash and cash equivalents	0.3	(0.5)
Cash and cash equivalents at beginning of period	0.0	0.5
Cash and cash equivalents at end of period	0.3	0.0
Reportable Legal Entities | Subsidiary Issuer
Statement of Cash Flows
Net cash provided by (used in) operating activities	(108.3)	(99.5)
Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from sale of operating assets	0.0	0.0
Proceeds from other recoveries		0.0
Advances to affiliates, net	(16.8)	(276.5)
Net cash provided by (used in) investing activities	(16.8)	(276.5)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	539.1	247.1
Repayment of borrowings from long-term debt and term loan		0.0
Proceeds from borrowings on revolving credit agreement	0.0	0.0
Repayment of borrowings on revolving credit agreement, including financing fees	(0.8)	(3.6)
Principal payment of capital lease obligation	0.0	0.0
Advances from affiliates, net	(306.2)	132.3
Distributions paid	0.0	0.0
Proceeds from sale of common units		0.0
Capital contributions from general partner		0.0
Net cash (used in) provided by financing activities	232.1	375.8
Increase (decrease) in cash and cash equivalents	107.0	(0.2)
Cash and cash equivalents at beginning of period	0.3	1.8
Cash and cash equivalents at end of period	107.3	1.6
Reportable Legal Entities | Non-Guarantor Subsidiaries
Statement of Cash Flows
Net cash provided by (used in) operating activities	535.2	509.3
Investing Activities:
Capital expenditures	(432.4)	(241.1)
Proceeds from sale of operating assets	0.2	0.3
Proceeds from other recoveries		6.2
Advances to affiliates, net	256.5	(71.4)
Net cash provided by (used in) investing activities	(175.7)	(306.0)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0.0	0.0
Repayment of borrowings from long-term debt and term loan		(725.0)
Proceeds from borrowings on revolving credit agreement	255.0	980.0
Repayment of borrowings on revolving credit agreement, including financing fees	(630.0)	(735.0)
Principal payment of capital lease obligation	(0.3)	(0.3)
Advances from affiliates, net	16.8	276.5
Distributions paid	0.0	0.0
Proceeds from sale of common units		0.0
Capital contributions from general partner		0.0
Net cash (used in) provided by financing activities	(358.5)	(203.8)
Increase (decrease) in cash and cash equivalents	1.0	(0.5)
Cash and cash equivalents at beginning of period	2.8	4.3
Cash and cash equivalents at end of period	3.8	3.8
Eliminations
Statement of Cash Flows
Net cash provided by (used in) operating activities	0.0	0.0
Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from sale of operating assets	0.0	0.0
Proceeds from other recoveries		0.0
Advances to affiliates, net	(289.4)	408.8
Net cash provided by (used in) investing activities	(289.4)	408.8
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0.0	0.0
Repayment of borrowings from long-term debt and term loan		0.0
Proceeds from borrowings on revolving credit agreement	0.0	0.0
Repayment of borrowings on revolving credit agreement, including financing fees	0.0	0.0
Principal payment of capital lease obligation	0.0	0.0
Advances from affiliates, net	289.4	(408.8)
Distributions paid	0.0	0.0
Proceeds from sale of common units		0.0
Capital contributions from general partner		0.0
Net cash (used in) provided by financing activities	289.4	(408.8)
Increase (decrease) in cash and cash equivalents	0.0	0.0
Cash and cash equivalents at beginning of period	0.0	0.0
Cash and cash equivalents at end of period	$ 0.0	$ 0.0