Guarantee of Securities of Subsidiaries Guarantee of Securities of Subsidiaries Statements of Cash Flows (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Statement of Cash Flows
Net cash provided by (used in) operating activities	$ 304.7	$ 285.5
Investing Activities:
Capital expenditures	(259.0)	(136.3)
Proceeds from sale of operating assets	0.1	0.1
Advances to affiliates, net	0.0	0.0
Net cash provided by (used in) investing activities	(258.9)	(136.2)
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	835.0
Repayment of borrowings on revolving credit agreement, including financing fees	(630.0)	(558.6)
Principal payment of capital lease obligation	(0.2)	(0.2)
Advances from affiliates, net	0.1	0.1
Distributions paid	(51.1)	(50.4)
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	112.9	(136.6)
Increase in cash and cash equivalents	158.7	12.7
Cash and cash equivalents at beginning of period	3.1	6.6
Cash and cash equivalents at end of period	161.8	19.3
Reportable Legal Entities | Parent Guarantor
Statement of Cash Flows
Net cash provided by (used in) operating activities	17.8	12.6
Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from sale of operating assets	0.0	0.0
Advances to affiliates, net	33.6	(77.7)
Net cash provided by (used in) investing activities	33.6	(77.7)
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	0.1	0.1
Distributions paid	(51.1)	(50.4)
Proceeds from sale of common units		113.1
Capital contributions from general partner		2.3
Net cash (used in) provided by financing activities	(51.0)	65.1
Increase in cash and cash equivalents	0.4	0.0
Cash and cash equivalents at beginning of period	0.0	0.5
Cash and cash equivalents at end of period	0.4	0.5
Reportable Legal Entities | Subsidiary Issuer
Statement of Cash Flows
Net cash provided by (used in) operating activities	(73.3)	(67.1)
Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from sale of operating assets	0.0	0.0
Advances to affiliates, net	(6.5)	(304.4)
Net cash provided by (used in) investing activities	(6.5)	(304.4)
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	0.0	(3.6)
Principal payment of capital lease obligation	0.0	0.0
Advances from affiliates, net	(303.7)	129.0
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	235.4	372.5
Increase in cash and cash equivalents	155.6	1.0
Cash and cash equivalents at beginning of period	0.3	1.8
Cash and cash equivalents at end of period	155.9	2.8
Reportable Legal Entities | Non-Guarantor Subsidiaries
Statement of Cash Flows
Net cash provided by (used in) operating activities	360.2	340.0
Investing Activities:
Capital expenditures	(259.0)	(136.3)
Proceeds from sale of operating assets	0.1	0.1
Advances to affiliates, net	270.1	(51.3)
Net cash provided by (used in) investing activities	11.2	(187.5)
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	835.0
Repayment of borrowings on revolving credit agreement, including financing fees	(630.0)	(555.0)
Principal payment of capital lease obligation	(0.2)	(0.2)
Advances from affiliates, net	6.5	304.4
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	(368.7)	(140.8)
Increase in cash and cash equivalents	2.7	11.7
Cash and cash equivalents at beginning of period	2.8	4.3
Cash and cash equivalents at end of period	5.5	16.0
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
Advances to affiliates, net	(297.2)	433.4
Net cash provided by (used in) investing activities	(297.2)	433.4
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	297.2	(433.4)
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	297.2	(433.4)
Increase 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