Fair value measurements (Percentages of total commodity sales excluding effects of hedging activities) (Details) - Customer Concentration Risk - Commodity Sales	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Coffeyville Resources LLC
Concentration Risk [Line Items]
Percentage of sales to significant purchaser		20.90%
Coffeyville Resources LLC | Predecessor
Concentration Risk [Line Items]
Percentage of sales to significant purchaser			19.30%
Phillips 66 Company
Concentration Risk [Line Items]
Percentage of sales to significant purchaser	26.00%	14.60%
Phillips 66 Company | Predecessor
Concentration Risk [Line Items]
Percentage of sales to significant purchaser			15.10%
Sunoco, Inc.
Concentration Risk [Line Items]
Percentage of sales to significant purchaser	7.20%	0.00%
Sunoco, Inc. | Predecessor
Concentration Risk [Line Items]
Percentage of sales to significant purchaser			0.00%
Alta Mesa Resources, Inc.
Concentration Risk [Line Items]
Percentage of sales to significant purchaser	6.70%	0.00%
Alta Mesa Resources, Inc. | Predecessor
Concentration Risk [Line Items]
Percentage of sales to significant purchaser			0.00%
Valero Energy Corporation
Concentration Risk [Line Items]
Percentage of sales to significant purchaser		13.30%
Valero Energy Corporation | Predecessor
Concentration Risk [Line Items]
Percentage of sales to significant purchaser			15.60%