Derivative Financial Instruments and Related Hedging Programs, Offsetting of Derivative Instruments by Counterparty (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	$ 90.6		$ 81.8
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	90.6		81.8
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	1.1		1.2
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	89.5		80.6
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(90.0)		(86.1)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(90.0)		(86.1)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(1.1)		(1.2)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	(88.9)		(84.9)
Counterparty (with Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	2.0		1.0
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	2.0		1.0
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	0.8		0.8
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	1.2		0.2
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(0.8)		(1.6)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(0.8)		(1.6)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(0.8)		(0.8)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	0		(0.8)
Counterparty (without Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	87.6	[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	87.6	[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	87.6	[1]	80.4	[1]
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(88.7)	[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	(88.7)	[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	(88.7)	[1]	(83.2)	[1]
Counterparty (with partial Netting Agreements)
Derivative Assets and Collateral Held by Counterparty
Gross Amounts of Recognized Assets	1.0		0.4
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	1.0		0.4
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	0.3		0.4
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Received	0		0
Net Amount	0.7		0
Derivative Liabilities and Collateral Held by Counterparty
Gross Amounts of Recognized Liabilities	(0.5)		(1.3)
Gross Amounts Offset in the Consolidated Balance Sheets	0		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	(0.5)		(1.3)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Financial Instruments	(0.3)		(0.4)
Gross Amounts Not Offset in the Consolidated Balance Sheets - Cash Collateral Pledged	0		0
Net Amount	$ (0.2)		$ (0.9)

[1] Such amounts include the fair value of the Bifurcated Conversion Feature and Call Options at June 30, 2014 (see Note 9).