Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value Summary of Long-Term Debt with Fixed Interest Rates

The following table summarizes the fair value of our long-term debt with fixed interest rates, which is estimated based on the published market prices for these debt obligations as of the dates presented:

	December 31, 2014				December 31, 2013
	Fair Value		Carrying Value		Fair Value		Carrying Value
Senior Notes due 2019	234,000		300,000		307,500		300,000
Senior Notes due 2020	620,000		775,000		837,969		775,000
	$	854,000	$	1,075,000	$	1,145,469	$	1,075,000

Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables summarize the valuation of those assets and liabilities as of the dates presented:

	As of December 31, 2014
	Fair Value			Fair Value Measurement Classification
Description	Measurement			Level 1			Level 2		Level 3
Assets:
Commodity derivative assets – current	$	128,981		$	—		$	128,981	$	—
Commodity derivative assets – noncurrent	35,897			—			35,897		—
Assets of SERP	4,123			4,123			—		—
Liabilities:
Deferred compensation – SERP obligation and other	(4,178		)	(4,178		)	—		—

	As of December 31, 2013
	Fair Value			Fair Value Measurement Classification
Description	Measurement			Level 1			Level 2			Level 3
Assets:
Commodity derivative assets – current	$	3,830		$	—		$	3,830		$	—
Commodity derivative assets – noncurrent	1,552			—			1,552			—
Assets of SERP	3,734			3,734			—			—
Liabilities:
Commodity derivative liabilities – noncurrent	(10,141		)	—			(10,141		)	—
Deferred compensation – SERP obligation and other	(3,879		)	(3,879		)	—			—