Fair Value Measurements (Fair Value Hierarchy Table) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Oil derivative contracts - current asset	$ 72,798	$ 142,846
Total Assets	72,798	142,846
Oil derivative contracts - current liability	25,005	0
Total Liabilities	25,005
Quoted Prices in Active Markets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Oil derivative contracts - current asset	0	0
Total Assets	0	0
Oil derivative contracts - current liability	0
Total Liabilities	0
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Oil derivative contracts - current asset	49,758	90,012
Total Assets	49,758	90,012
Oil derivative contracts - current liability	25,005
Total Liabilities	25,005
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Oil derivative contracts - current asset	23,040	52,834
Total Assets	23,040	$ 52,834
Oil derivative contracts - current liability	0
Total Liabilities	$ 0