Pushdown Accounting (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		5 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Jun. 03, 2014	Dec. 31, 2014	Mar. 31, 2015	Jun. 30, 2015	Dec. 31, 2013	Dec. 31, 2012
Tax rate used to recognize deferred income taxes							37.00%
Amount reimbursed to Chevron after the acquisition		$ 2,100			$ 2,100		$ 2,100
Increase in value of goodwill		2,100			$ 2,100		$ 2,100
Statutory federal income tax rate	35.00%			35.00%	35.00%	35.00%	35.00%	35.00%	35.00%
Statutory state tax rate, net of federal tax rate							2.00%
Goodwill impairment		$ 329,293	$ 12