Description of Business and Accounting Policies Description of Business and Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 D	Dec. 31, 2011	Dec. 31, 2010	Jan. 24, 2013
Description of accounting policies [Line Items]
Percent of Revenue from Foreign Subsidiaries	1.00%
Number of Segments	4
Investment owned in CyrusOne Inc., Balance, Shares				1.9
Investment owned in CyrusOne Inc., Percentage				8.60%
Investment in CyrusOne LP, Balance, Partnership Units				42.6
Investment owned in CyrusOne LP, Percentage				66.00%
Total ownership interests in CyrusOne, Percentage				69.00%
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	$ 26.0	$ 26.8
Cost Method Investments	2.7	2.9
Advertising Expense	16.6	18.4	22.0
Regulatory Taxes Included in Revenue	22.2	20.6	19.9
Regulatory Taxes Included in Expense	$ 24.4	$ 22.7	$ 22.0
Pension Plans, Defined Benefit [Member]
Description of accounting policies [Line Items]
Lower range in years of remaining service life of active employees	10
Upper range in years of remaining service life of active employees	14
Other Postretirement Benefit Plans, Defined Benefit [Member]
Description of accounting policies [Line Items]
Lower range in years of remaining service life of active employees	17