Guarantee of Securities of Subsidiaries Guarantee of Securities of Subsidiaries Statements of Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 77.7	$ 25.6
Other comprehensive income (loss):
Loss on cash flow hedges	0	(0.9)
Reclassification adjustment transferred to Net Income from cash flow hedges	0.6	0.9
Pension and other postretirement benefit costs	(2.1)	(1.9)
Total Comprehensive Income (Loss)	76.2	23.7
Comprehensive loss attributable to noncontrolling interests	0	(84.6)
Comprehensive income (loss) attributable to controlling interests	76.2	108.3
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(175.4)	(233.7)
Other comprehensive income (loss):
Loss on cash flow hedges		1.8
Reclassification adjustment transferred to Net Income from cash flow hedges	(0.8)	(1.4)
Pension and other postretirement benefit costs	4.2	3.8
Total Comprehensive Income (Loss)		(229.5)
Comprehensive loss attributable to noncontrolling interests		0
Comprehensive income (loss) attributable to controlling interests	(172.0)	(229.5)
Parent Guarantor | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	77.7	110.2
Other comprehensive income (loss):
Loss on cash flow hedges		(0.9)
Reclassification adjustment transferred to Net Income from cash flow hedges	0.6	0.9
Pension and other postretirement benefit costs	(2.1)	(1.9)
Total Comprehensive Income (Loss)		108.3
Comprehensive loss attributable to noncontrolling interests		0
Comprehensive income (loss) attributable to controlling interests	76.2	108.3
Subsidiary Issuer | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	71.0	102.4
Other comprehensive income (loss):
Loss on cash flow hedges		(0.9)
Reclassification adjustment transferred to Net Income from cash flow hedges	0.6	0.9
Pension and other postretirement benefit costs	(2.1)	(1.9)
Total Comprehensive Income (Loss)		100.5
Comprehensive loss attributable to noncontrolling interests		0
Comprehensive income (loss) attributable to controlling interests	69.5	100.5
Non-Guarantor Subsidiaries | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	104.4	46.7
Other comprehensive income (loss):
Loss on cash flow hedges		(0.9)
Reclassification adjustment transferred to Net Income from cash flow hedges	0.2	0.5
Pension and other postretirement benefit costs	(2.1)	(1.9)
Total Comprehensive Income (Loss)		44.4
Comprehensive loss attributable to noncontrolling interests		(84.6)
Comprehensive income (loss) attributable to controlling interests	$ 102.5	$ 129.0