Revenue from Contract with Customers (Narrative) (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
Average Delivery Point of Barrels in Pipeline System	50.00%	50.00%
Deferred Revenue, Revenue Recognized	$ 10.7	$ 77.0

Amount of revenue recognized that was previously reported as deferred or unearned revenue.

No definition available.

Name:	us-gaap_DeferredRevenueRevenueRecognized1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration