Derivative Financial Instruments and Related Hedging Programs, Offsetting of Derivative Instruments by Counterparty (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	$ 84.3		$ 58.5
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	84.3		58.5
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	0.9		1.2
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	83.4		57.3
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(94.8)		(66.7)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(94.8)		(66.7)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(0.9)		(1.2)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	93.9		65.5
Counterparty (with Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	0.7		2.3
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	0.7		2.3
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	0.6		1.0
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	0.1		1.3
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(2.8)		(1.7)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(2.8)		(1.7)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(0.6)		(1.0)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	2.2		0.7
Counterparty (without Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	83.3	[1]	55.9	[1]
Gross Amounts Offset in the Consolidated Balance Sheets	0	[1]	0	[1]
Net Amounts of Assets Presented in the Consolidated Balance Sheets	83.3	[1]	55.9	[1]
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	0	[1]	0	[1]
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0	[1]	0	[1]
Net Amount	83.3	[1]	55.9	[1]
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(90.3)	[1]	(63.8)	[1]
Gross Amounts Offset in the Consolidated Balance Sheets	0	[1]	0	[1]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(90.3)	[1]	(63.8)	[1]
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	0	[1]	0	[1]
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0	[1]	0	[1]
Net Amount	90.3	[1]	63.8	[1]
Counterparty (with partial Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	0.3		0.3
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	0.3		0.3
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	0.3		0.2
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	0		0.1
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(1.7)		(1.2)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(1.7)		(1.2)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(0.3)		(0.2)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	$ 1.4		$ 1.0

[1] Such amounts include the fair value of the Bifurcated Conversion Feature and Call Options at September 30, 2013 (see Note 10).