Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 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:

	As of
	June 30, 2014				December 31, 2013
	Fair Value		Carrying Value		Fair Value		Carrying Value
Senior Notes due 2019	$	315,000	$	300,000	$	307,500	$	300,000
Senior Notes due 2020	864,125		775,000		837,969		775,000
	$	1,179,125	$	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 June 30, 2014
	Fair Value			Fair Value Measurement Classification
Description	Measurement			Level 1			Level 2			Level 3
Assets:
Commodity derivative assets - current	$	—		$	—		$	—		$	—
Commodity derivative assets - noncurrent	—			—			—			—
Assets of SERP	3,951			3,951			—			—
Liabilities:
Commodity derivative liabilities - current	(44,298		)	—			(44,298		)	—
Commodity derivative liabilities - noncurrent	(8,508		)	—			(8,508		)	—
Deferred compensation - SERP obligations	(4,211		)	(4,211		)	—			—

	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 - current	(10,141		)	—			(10,141		)	—
Deferred compensation - SERP obligations	(3,879		)	(3,879		)	—			—