Restricted Securities Available For Sale (Schedule Of Cost And Estimated Fair Values Of Debt Securities By Contractual Maturity) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Total restricted securities available for sale	$ 47.5	$ 46.1
Cost [Member]
Summary Of Significant Accounting Policies [Line Items]
Within one year	35.0	33.8
Over one year to five years	8.9	8.6
Over five years to ten years	3.7	3.9
Total restricted securities available for sale	47.6	46.3
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Within one year	34.9	33.7
Over one year to five years	8.9	8.6
Over five years to ten years	3.7	3.8
Total restricted securities available for sale	$ 47.5	$ 46.1