Financial Instruments and Fair Value (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jul. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total carrying value	$ 416.1		$ 416.1		$ 458.6
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total carrying value	358.2		358.2		357.9
Portion at Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total fair value	378.8		378.8		361.4
Senior Subordinated Convertible Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate of debt instrument	3.00%		3.00%
8.375% Senior Subordinated Notes due 2020 | Senior Subordinated Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate of debt instrument	8.375%		8.375%		8.375%
Total carrying value	200.0		200.0		200.0
Total fair value	217.0		217.0		205.0
7.625% Senior Subordinated Notes due 2017 | Senior Subordinated Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate of debt instrument	7.625%		7.625%		7.625%
Total carrying value	143.2		143.2		143.2
Total fair value	146.8		146.8		141.8
3% Senior Subordinated Convertible Notes due 2012 | Senior Subordinated Convertible Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate of debt instrument	3.00%		3.00%		3.00%
Discount of debt instrument	0.1		0.1		0.4
Face value of debt instrument	15.1		15.1		15.1
Total carrying value	15.0		15.0		14.7
Total fair value	15.0		15.0		14.6
Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional principal amount of interest rate swap agreement	20.4		20.4		21.0	21.5
Notional principal amount of interest rate swap agreement, at maturity	16.1		16.1
Results Recognized in AOCI (Effective Portion)	(0.1)	(1.7)	(0.2)	(1.7)
Interest rate swap, amount expected to be reclassified in the next twelve months	4.4		4.4
Underlying Rate			1 month LIBOR		1 month LIBOR
Expiration			Oct. 01, 2015		Oct. 01, 2015
Fair value of interest rate swaps	0.6		0.6		0.5
Interest Expense [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount Reclassified out of AOCI to Earnings	0	(1.3)	(0.1)	(2.7)
Ineffective Results Recognized in Earnings	0	0	0	0
Interest Expense [Member] | Terminated Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount Reclassified out of AOCI to Earnings	(1.2)	(0.1)	(2.4)	(0.1)
Accounts Payable [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of interest rate swaps	0.2		0.2		0.2
Accrued Liabilities [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of interest rate swaps	$ 0.4		$ 0.4		$ 0.3