Accounts Receivable, Net of Allowance (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables, Non-Recourse Arrangement [Member] \| Interest Expense, Net [Member]
Schedule of Accounts Receivable, Net of Allowance [Line Items]
Non-recourse financing arrangement, discount charge	$ 6.0	$ 2.7	$ 1.6

Reflects the net positive or negative amount derived from subtracting from net proceeds of sale, the carrying amounts, net of allocated reserves, of accounts receivable transferred to a third party in a transaction that qualifies for sales treatment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=82924980&loc=d3e107425-111719

Name:	us-gaap_GainLossOnSaleOfAccountsReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration