Nature Of Operations And Significant Accounting Policies (Summary Of Allowance For Doubtful Accounts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	$ 4.7	$ 4.9	$ 4.8
Provision for Loan, Lease, and Other Losses	6.1	3.0	3.7
Financing Receivable, Allowance for Credit Losses, Write-downs	(3.5)	(3.2)	(3.6)
Balance at end of year	$ 7.3	$ 4.7	$ 4.9