Principles Of Preparation (Accrued Unbilled Revenues) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accrued unbilled revenues	$ 20.0	$ 22.2

Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements due within one year or the normal operating cycle, if longer.

No definition available.

Name:	us-gaap_UnbilledReceivablesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant