Significant Accounting Policies (Concentraction Risk) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 item
Concentration Risk [Line Items]
Allowance for Doubtful Accounts Receivable | $	$ 0.1	$ 0.3
Customer Concentration Risk | Sales Revenue, Net | Devon Energy Corporation
Concentration Risk [Line Items]
Concentration Risk, Percentage	18.50%	16.60%	30.60%
Louisiana Operating Segment | Customer Concentration Risk | Sales Revenue, Net | Third Party
Concentration Risk [Line Items]
Number of customers | item	1	1	1
Concentration Risk, Percentage	10.80%	11.70%	11.00%