Description of Business and Accounting Policies Description of Business and Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 D	Dec. 31, 2010	Dec. 31, 2009
Description of accounting policies [Line Items]
Percent of Revenue from Foreign Subsidiaries	1.00%
Number of Segments	4
Trade Receivables Due From Customers, Range, Minimum	21
Trade Receivables Due from Customers, Range, Maximum	90
Number of customers, exceeds 10% of total accounts receivables	1
Unbilled Receivables, Current	$ 26.8	$ 25.1
Cost Method Investments	2.9	3.1
Advertising Expense	18.4	22.0	22.8
Regulatory Taxes Included in Revenue	20.6	19.9	16.7
Regulatory Taxes Included in Expense	$ 22.7	$ 22.0	$ 17.2
Pension Plans, Defined Benefit [Member]
Description of accounting policies [Line Items]
minumum number of years other comprehensive loss amortizated in	10
maximum number of years other comprehensive loss amortized in	14
Other Postretirement Benefit Plans, Defined Benefit [Member]
Description of accounting policies [Line Items]
minumum number of years other comprehensive loss amortizated in	16