Summary of Significant Accounting Policies (Concentration of Credit Risk Narrative) (Details) (Customer Concentration Risk [Member])	12 Months Ended
	Dec. 31, 2014 customers	Dec. 31, 2012 customers	Dec. 31, 2013 customers
Sales Revenue [Member] | First Largest Customer [Member]
Concentration Risk [Line Items]
Concentration risk, number of customers	1	1
Concentration risk, percent	19.00%	17.00%
Sales Revenue [Member] | McLane [Member]
Concentration Risk [Line Items]
Concentration risk, number of customers			2
Concentration risk, percent			18.00%
Sales Revenue [Member] | Core Mark [Member]
Concentration Risk [Line Items]
Concentration risk, number of customers			2
Concentration risk, percent			10.00%
Accounts Receivable [Member] | First Largest Customer [Member]
Concentration Risk [Line Items]
Concentration risk, percent	11.00%	10.00%
Accounts Receivable [Member] | McLane [Member]
Concentration Risk [Line Items]
Concentration risk, number of customers			2
Concentration risk, percent			5.00%
Accounts Receivable [Member] | Core Mark [Member]
Concentration Risk [Line Items]
Concentration risk, number of customers			2
Concentration risk, percent			1.00%