Guarantee of Securities of Subsidiaries Guarantee of Securities of Subsidiaries Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Cash Flows
Net cash provided by (used in) operating activities	$ 122.3	$ 146.8
Investing Activities:
Capital expenditures	(105.6)	(62.2)
Proceeds from sale of operating assets	0.1	0.0
Advances to affiliates, net	0.0	0.0
Net cash provided by (used in) investing activities	(105.5)	(62.2)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0.0	247.1
Repayment of borrowings from long-term debt and term loan	0.0	(300.0)
Proceeds from borrowings on revolving credit agreement	175.0	340.0
Repayment of borrowings on revolving credit agreement	(160.0)	(410.0)
Principal payment of capital lease obligation	(0.1)	(0.1)
Advances from affiliates, net	0.0	0.0
Distributions paid	(25.5)	(24.8)
Proceeds from sale of common units	0.0	83.2
Capital contributions from general partner	0.0	2.2
Net cash (used in) provided by financing activities	(10.6)	(62.4)
Increase in cash and cash equivalents	6.2	22.2
Cash and cash equivalents at beginning of period	3.1	6.6
Cash and cash equivalents at end of period	9.3	28.8
Reportable Legal Entities | Parent Guarantor
Statement of Cash Flows
Net cash provided by (used in) operating activities	8.9	6.2
Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from sale of operating assets	0.0
Advances to affiliates, net	16.8	(60.7)
Net cash provided by (used in) investing activities	16.8	(60.7)
Financing Activities:
Proceeds from long-term debt, net of issuance cost		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	0.0	0.0
Principal payment of capital lease obligation	0.0	0.0
Advances from affiliates, net	0.0	0.0
Distributions paid	(25.5)	(24.8)
Proceeds from sale of common units		83.2
Capital contributions from general partner		2.2
Net cash (used in) provided by financing activities	(25.5)	60.6
Increase in cash and cash equivalents	0.2	6.1
Cash and cash equivalents at beginning of period	0.0	0.5
Cash and cash equivalents at end of period	0.2	6.6
Reportable Legal Entities | Subsidiary Issuer
Statement of Cash Flows
Net cash provided by (used in) operating activities	(35.1)	(28.9)
Investing Activities:
Capital expenditures	0.0	0.0
Proceeds from sale of operating assets	0.0
Advances to affiliates, net	(0.9)	(139.8)
Net cash provided by (used in) investing activities	(0.9)	(139.8)
Financing Activities:
Proceeds from long-term debt, net of issuance cost		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	0.0	0.0
Principal payment of capital lease obligation	0.0	0.0
Advances from affiliates, net	41.1	(64.8)
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	41.1	182.3
Increase in cash and cash equivalents	5.1	13.6
Cash and cash equivalents at beginning of period	0.3	1.8
Cash and cash equivalents at end of period	5.4	15.4
Reportable Legal Entities | Non-Guarantor Subsidiaries
Statement of Cash Flows
Net cash provided by (used in) operating activities	148.5	169.5
Investing Activities:
Capital expenditures	(105.6)	(62.2)
Proceeds from sale of operating assets	0.1
Advances to affiliates, net	(57.9)	125.5
Net cash provided by (used in) investing activities	(163.4)	63.3
Financing Activities:
Proceeds from long-term debt, net of issuance cost		0.0
Repayment of borrowings from long-term debt and term loan		(300.0)
Proceeds from borrowings on revolving credit agreement	175.0	340.0
Repayment of borrowings on revolving credit agreement	(160.0)	(410.0)
Principal payment of capital lease obligation	(0.1)	(0.1)
Advances from affiliates, net	0.9	139.8
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	15.8	(230.3)
Increase in cash and cash equivalents	0.9	2.5
Cash and cash equivalents at beginning of period	2.8	4.3
Cash and cash equivalents at end of period	3.7	6.8
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
Advances to affiliates, net	42.0	75.0
Net cash provided by (used in) investing activities	42.0	75.0
Financing Activities:
Proceeds from long-term debt, net of issuance cost		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	0.0	0.0
Principal payment of capital lease obligation	0.0	0.0
Advances from affiliates, net	(42.0)	(75.0)
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	(42.0)	(75.0)
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