Derivative Financial Instruments and Related Hedging Programs, Offsetting of Derivative Instruments by Counterparty (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	$ 88.3		$ 81.8
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	88.3		81.8
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	1.8		1.2
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	86.5		80.6
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(89.7)		(86.1)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(89.7)		(86.1)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(1.8)		(1.2)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	(87.9)		(84.9)
Counterparty (with Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	1.4		1.0
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	1.4		1.0
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	1.2		0.8
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	0.2		0.2
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(1.9)		(1.6)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(1.9)		(1.6)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(1.2)		(0.8)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	(0.7)		(0.8)
Counterparty (without Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	85.7	[1]	80.4	[1]
Gross Amounts Offset in the Consolidated Balance Sheets	0	[1]	0	[1]
Net Amounts of Assets Presented in the Consolidated Balance Sheets	85.7	[1]	80.4	[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	85.7	[1]	80.4	[1]
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(86.9)	[1]	(83.2)	[1]
Gross Amounts Offset in the Consolidated Balance Sheets	0	[1]	0	[1]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(86.9)	[1]	(83.2)	[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	(86.9)	[1]	(83.2)	[1]
Counterparty (with partial Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	1.2		0.4
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	1.2		0.4
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	0.6		0.4
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	0.6		0
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(0.9)		(1.3)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(0.9)		(1.3)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(0.6)		(0.4)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	$ (0.3)		$ (0.9)

[1] Such amounts include the fair value of the Bifurcated Conversion Feature and Call Options at March 31, 2014 (see Note 9).