Accounts Receivable (Narrative) (Details) $ in Millions	9 Months Ended
Sep. 30, 2017 USD ($)
Accounts Receivable [Abstract]
Allowance for Doubtful Accounts Receivable, Recoveries	$ 35

Amount of recoveries of receivables doubtful of collection that were previously charged off.

No definition available.

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