Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Income Taxes [Abstract]
Net deferred tax liabilities	$ 119.3	$ 123.7
Valuation allowance	0
Unrecognized tax benefits	$ 0		$ 0

The amount as of the balance sheet date of the estimated future tax effects attributable to items expensed for tax purposes but capitalized in conformity with generally accepted accounting principles, which will reverse in future periods when amortization of such capitalized costs cannot be deducted for tax purposes.

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The amount of the valuation allowance recorded as of the balance sheet date pertaining to the specified deferred tax asset for which an assessment was made that it is more likely than not that all or a portion of such deferred tax asset will not be realized through related deductions on future tax returns.

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