Derivative Financial Instruments - Summary of Gross and Net Information About Commodity Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments Gain Loss [Line Items]
Unrealized gain on commodity contracts			$ 344	$ 1,155
Net gain (loss) on derivative contracts	$ 5,166	$ 2,489	4,522	186
Derivatives Not Designated as Hedging Contracts [Member] | Net Gain (Loss) On Derivative Contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Unrealized gain on commodity contracts	3,425	2,369	344	1,155
Realized gain (loss) on commodity contracts	$ 1,741	$ 120	$ 4,178	$ (969)