Fair Value Measurements (Derivative Assets and Contingent Consideration Measured at Fair Value) (Details) - USD ($) $ in Thousands | Jun. 30, 2015 | Dec. 31, 2014 | Jun. 30, 2014 | [1] | Mar. 31, 2014 | Dec. 31, 2013 |
Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | | $ 0 | $ (2,843) | $ (2,517) |
Fair Value, Measurements, Recurring [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | $ 1,884 | | | | |
Contingent consideration | | $ (23,330) | | | |
Total | | (13,264) | | | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 0 | | | | |
Contingent consideration | | 0 | | | |
Total | | 0 | | | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 1,884 | | | | |
Contingent consideration | | 0 | | | |
Total | | 10,066 | | | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 0 | | | | |
Contingent consideration | | (23,330) | | | |
Total | | (23,330) | | | |
Fair Value, Measurements, Recurring [Member] | Oil And Natural Gas Collars [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 667 | | | | |
Fair Value, Measurements, Recurring [Member] | Oil And Natural Gas Collars [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 0 | | | | |
Fair Value, Measurements, Recurring [Member] | Oil And Natural Gas Collars [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 667 | | | | |
Fair Value, Measurements, Recurring [Member] | Oil And Natural Gas Collars [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 0 | | | | |
Fair Value, Measurements, Recurring [Member] | Natural Gas and NGL Puts [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 140 | | | | |
Fair Value, Measurements, Recurring [Member] | Natural Gas and NGL Puts [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 0 | | | | |
Fair Value, Measurements, Recurring [Member] | Natural Gas and NGL Puts [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 140 | | | | |
Fair Value, Measurements, Recurring [Member] | Natural Gas and NGL Puts [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 0 | | | | |
Fair Value, Measurements, Recurring [Member] | Oil, Natural Gas and NGL Swaps [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 1,077 | | | | |
Fair Value, Measurements, Recurring [Member] | Oil, Natural Gas and NGL Swaps [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 0 | | | | |
Fair Value, Measurements, Recurring [Member] | Oil, Natural Gas and NGL Swaps [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | 1,077 | | | | |
Fair Value, Measurements, Recurring [Member] | Oil, Natural Gas and NGL Swaps [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | $ 0 | | | | |
Fair Value, Measurements, Recurring [Member] | Oil Collar [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 2,411 | | | |
Fair Value, Measurements, Recurring [Member] | Oil Collar [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 0 | | | |
Fair Value, Measurements, Recurring [Member] | Oil Collar [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 2,411 | | | |
Fair Value, Measurements, Recurring [Member] | Oil Collar [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 0 | | | |
Fair Value, Measurements, Recurring [Member] | Natural Gas Collars [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 1,405 | | | |
Fair Value, Measurements, Recurring [Member] | Natural Gas Collars [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 0 | | | |
Fair Value, Measurements, Recurring [Member] | Natural Gas Collars [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 1,405 | | | |
Fair Value, Measurements, Recurring [Member] | Natural Gas Collars [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 0 | | | |
Fair Value, Measurements, Recurring [Member] | Oil Put Options [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 6,250 | | | |
Fair Value, Measurements, Recurring [Member] | Oil Put Options [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 0 | | | |
Fair Value, Measurements, Recurring [Member] | Oil Put Options [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | 6,250 | | | |
Fair Value, Measurements, Recurring [Member] | Oil Put Options [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | | |
Net fair value of derivative | | $ 0 | | | |
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[1] | Fair values related to the Company’s natural gas collars, natural gas and NGL put options and NGL fixed price swaps were transferred from Level 3 to Level 2 in the second quarter of 2014 due to enhancements to the Company’s internal valuation process, including the use of observable inputs to assess the fair value. |