Cimarex Energy (CIMXP) 10-Q 6 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013
Document and Entity Information	'
Entity Registrant Name	'CIMAREX ENERGY CO
Entity Central Index Key	'0001168054
Document Type	'10-Q
Document Period End Date	30-Sep-13
Amendment Flag	'false
Current Fiscal Year End Date	'--12-31
Entity Current Reporting Status	'Yes
Entity Filer Category	'Large Accelerated Filer
Entity Common Stock, Shares Outstanding	86,838,423
Document Fiscal Year Focus	'2013
Document Fiscal Period Focus	'Q3

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$4,531	$69,538
Restricted cash	818	'
Receivables, net	391,105	302,974
Oil and gas well equipment and supplies	69,517	81,029
Deferred income taxes	13,902	8,477
Derivative instruments	7,168	'
Prepaid expenses	5,750	7,420
Other current assets	4,082	699
Total current assets	496,873	470,137
Oil and gas properties at cost, using the full cost method of accounting:	'	'
Proved properties	12,466,073	11,258,748
Unproved properties and properties under development, not being amortized	597,526	645,078
Gross oil and gas properties	13,063,599	11,903,826
Less - accumulated depreciation, depletion and amortization	-7,318,137	-6,899,057
Net oil and gas properties	5,745,462	5,004,769
Fixed assets, net	137,455	152,605
Goodwill	620,232	620,232
Derivative instruments	2,717	'
Other assets, net	51,625	57,409
Total assets	7,054,364	6,305,152
Current liabilities:	'	'
Accounts payable	111,082	103,653
Accrued liabilities	403,413	392,909
Derivative instruments	4,320	'
Revenue payable	187,065	149,300
Total current liabilities	705,880	645,862
Long-term debt	900,000	750,000
Deferred income taxes	1,338,623	1,121,353
Other liabilities	293,576	313,201
Total liabilities	3,238,079	2,830,416
Stockholders' equity:	'	'
Preferred stock, $0.01 par value, 15,000,000 shares authorized, no shares issued	'	'
Common stock, $0.01 par value, 200,000,000 shares authorized, 86,838,423 and 86,595,976 shares issued, respectively	868	866
Paid-in capital	1,959,160	1,939,628
Retained earnings	1,855,382	1,533,768
Accumulated other comprehensive income	875	474
Total stockholders' equity	3,816,285	3,474,736
Total liabilities and stockholders' equity	$7,054,364	$6,305,152

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Condensed Consolidated Balance Sheets	'	'
Preferred stock, par value (in dollars per share)	$0.01	$0.01
Preferred stock, shares authorized	15,000,000	15,000,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	86,838,423	86,595,976

Consolidated_Statements_of_Inc

Consolidated Statements of Income and Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues:	'	'	'	'
Gas sales	$118,824	$83,208	$346,492	$238,102
Oil sales	371,881	263,315	933,879	759,609
NGL sales	58,922	50,860	168,106	154,160
Gas gathering, processing and other	11,380	10,054	32,951	31,940
Gas marketing, net	329	-525	21	-741
Total revenues	561,336	406,912	1,481,449	1,183,070
Costs and expenses:	'	'	'	'
Depreciation, depletion and amortization	159,182	135,987	442,851	375,486
Asset retirement obligation	1,797	3,512	7,080	9,478
Production	76,166	62,699	214,985	192,818
Transportation and other operating	25,838	14,481	66,494	40,966
Gas gathering and processing	6,970	5,496	18,310	15,302
Taxes other than income	31,104	24,095	84,039	72,738
General and administrative	19,003	14,742	57,416	41,523
Stock compensation	3,347	8,301	10,459	17,519
(Gain) loss on derivative instruments, net	10,824	5,329	-1,233	-661
Other operating, net	2,507	2,236	7,804	7,295
Total costs and expenses	336,738	276,878	908,205	772,464
Operating income	224,598	130,034	573,244	410,606
Other (income) and expense:	'	'	'	'
Interest expense	13,954	13,223	41,272	35,570
Capitalized interest	-7,286	-9,231	-23,868	-26,154
Loss on early extinguishment of debt	'	'	'	16,214
Other, net	-2,263	-6,159	-13,637	-18,714
Income before income tax	220,193	132,201	569,477	403,690
Income tax expense	81,823	47,939	211,615	149,019
Net income	138,370	84,262	357,862	254,671
Basic	'	'	'	'
Distributed (in dollars per share)	$0.14	$0.12	$0.42	$0.36
Undistributed (in dollars per share)	$1.45	$0.85	$3.70	$2.58
Total basic (in dollars per share)	$1.59	$0.97	$4.12	$2.94
Diluted	'	'	'	'
Distributed (in dollars per share)	$0.14	$0.12	$0.42	$0.36
Undistributed (in dollars per share)	$1.45	$0.85	$3.70	$2.57
Total diluted (in dollars per share)	$1.59	$0.97	$4.12	$2.93
Comprehensive income:	'	'	'	'
Net income	138,370	84,262	357,862	254,671
Other comprehensive income:	'	'	'	'
Change in fair value of investments, net of tax	302	238	401	502
Total comprehensive income	$138,672	$84,500	$358,263	$255,173

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:	'	'
Net income	$357,862	$254,671
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation, depletion and amortization	442,851	375,486
Asset retirement obligation	7,080	9,478
Deferred income taxes	211,615	150,648
Stock compensation	10,459	17,519
Gain on derivative instruments	-1,233	-661
Settlements on derivative instruments	-4,332	'
Loss on early extinguishment of debt	'	16,214
Changes in non-current assets and liabilities	9,102	7,930
Other, net	-685	3,354
Changes in operating assets and liabilities:	'	'
Receivables, net	-88,131	24,398
Other current assets	9,799	8,763
Accounts payable and accrued liabilities	-13,639	-31,652
Net cash provided by operating activities	940,748	836,148
Cash flows from investing activities:	'	'
Oil and gas expenditures	-1,165,555	-1,181,742
Sales of oil and gas assets	37,707	12,167
Sales of other assets	31,252	550
Other expenditures	-34,657	-42,913
Net cash used by investing activities	-1,131,253	-1,211,938
Cash flows from financing activities:	'	'
Net bank debt borrowings	150,000	25,000
Proceeds from other long-term debt	'	750,000
Other long-term debt payments	'	-363,595
Financing costs incurred	-100	-13,821
Dividends paid	-34,570	-29,199
Issuance of common stock and other	10,168	10,410
Net cash provided by financing activities	125,498	378,795
Net change in cash and cash equivalents	-65,007	3,005
Cash and cash equivalents at beginning of period	69,538	2,406
Cash and cash equivalents at end of period	$4,531	$5,411

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2013
Basis of Presentation	'
Basis of Presentation	'
	1.              Basis of Presentation
	The accompanying unaudited financial statements have been prepared by Cimarex Energy Co. (“Cimarex”, “we”, or “us”) pursuant to rules and regulations of the Securities and Exchange Commission (SEC).  Accordingly, certain disclosures required by accounting principles generally accepted in the United States and normally included in annual reports on Form 10-K have been omitted.  Although management believes that our disclosures in these interim financial statements are adequate, they should be read in conjunction with the financial statements, summary of significant accounting policies, and footnotes included in our 2012 Annual Report on Form 10-K.
	In the opinion of management, the accompanying financial statements reflect all adjustments necessary to present fairly our financial position, results of operations, and cash flows for the periods and as of the dates shown.  Certain amounts in prior years’ financial statements have been reclassified to conform to the 2012 financial statement presentation.  We have evaluated subsequent events through the date of this filing.
	Restricted Cash
	At December 31, 2012, we had restricted cash of $811 thousand included in our non-current other assets which consisted of monies from third parties that were being held by Cimarex, as operator of a property in Oklahoma, until the ownership disputes among the third parties could be resolved.  As of September 30, 2013, the ownership disputes have been resolved and we have transferred the restricted cash and the related liability from non-current to current.
	Oil and Gas Properties
	We use the full cost method of accounting for our oil and gas operations.  Accounting rules require us to perform a quarterly “ceiling test” calculation to test our oil and gas properties for possible impairment.  The primary components impacting this calculation are commodity prices, reserve quantities added and produced, overall exploration and development costs, depletion expense, and tax effects.  If the net capitalized cost of our oil and gas properties subject to amortization (the carrying value) exceeds the ceiling limitation, the excess would be charged to expense.  The ceiling limitation is equal to the sum of the present value discounted at 10% of estimated future net cash flows from proved reserves, the cost of properties not being amortized, the lower of cost or estimated fair value of unproven properties included in the costs being amortized, and all related tax effects.
	At September 30, 2013, the calculated value of the ceiling limitation exceeded the carrying value of our oil and gas properties subject to the test, and no impairment was necessary.  Our ceiling limitation has improved since December 31, 2012.  However, a decline of 5% in the value of the ceiling limitation would have resulted in an impairment.  If pricing conditions decline, or if there is a negative impact on one or more of the other components of the calculation, we may incur a full cost ceiling impairment related to our oil and gas properties in future quarters.
	Use of Estimates
	The more significant areas requiring the use of management’s estimates and judgments relate to the estimation of proved oil and gas reserves, the use of these oil and gas reserves in calculating depletion, depreciation, and amortization (DD&A), the use of the estimates of future net revenues in computing ceiling test limitations and estimates of future abandonment obligations used in recording asset retirement obligations, and the assessment of goodwill.  Estimates and judgments are also required in determining allowance for bad debt, impairments of undeveloped properties and other assets, purchase price allocation, valuation of deferred tax assets, fair value measurements, and commitments and contingencies.
	Accounts Receivable, Accounts Payable, and Accrued Liabilities
	The components of our receivable accounts, accounts payable, and accrued liabilities are shown below:
	(in thousands)	September 30,		December 31,
		2013		2012
	Receivables, net of allowance
	Trade	$	87,069	$	55,528
	Oil and gas sales	289,673		239,106
	Gas gathering, processing, and marketing	14,363		7,901
	Other	—		439
	Receivables, net	$	391,105	$	302,974
	Accounts payable
	Trade	$	84,152	$	88,168
	Gas gathering, processing, and marketing	26,930		15,485
	Accounts payable	$	111,082	$	103,653
	Accrued liabilities
	Exploration and development	$	173,066	$	155,002
	Taxes other than income	29,022		29,179
	Other	201,325		208,728
	Accrued liabilities	$	403,413	$	392,909
	Recently Issued Accounting Standards
	No significant accounting standards applicable to Cimarex have been issued during the quarter ended September 30, 2013.

Derivative_InstrumentsHedging

Derivative Instruments/Hedging	9 Months Ended
	Sep. 30, 2013
Derivative Instruments/Hedging	'
Derivative Instruments/Hedging	'
	2.                                      Derivative Instruments/Hedging
	We periodically enter into derivative instruments to mitigate a portion of our potential exposure to a decline in commodity prices and the corresponding negative impact on cash flow available for reinvestment.  While the use of these instruments limits the downside risk of adverse price changes, their use may also limit future revenues from favorable price changes.
	The following tables summarize our outstanding hedging contracts as of September 30, 2013:
	Oil Contracts
								Weighted Average Price							Fair Value
	Period	Type		Volume/Day		Index(1)		Floor			Ceiling		Swap		(in thousands)
	Oct 13 – Dec 13	Collars		6,000 Bbls		WTI		$	85		$	102.31	N/A		$	(1,311	)
	Oct 13 – Dec 13	Swaps		6,000 Bbls		WTI		N/A			N/A		$	96.13	$	(2,987	)
	Jan 14 – Dec 14	Collars		6,000 Bbls		WTI		$	85		$	105.68	N/A		$	1,477
	(1)         WTI refers to West Texas Intermediate price as quoted on the New York Mercantile Exchange.
	Gas Contracts
								Weighted Average					Fair Value
								Price
	Period	Type		Volume/Day		Index(1)		Floor			Ceiling		(in thousands)
	Oct 13 – Dec 14	Collars		80,000 MMBtu		PEPL		$	3.51		$	4.57	$	8,386
	(1)                PEPL refers to Panhandle Eastern Pipe Line, Tex/OK Mid-Continent Index as quoted in Platt’s Inside FERC.
	Under a collar agreement, we receive the difference between the published index price and a floor price if the index price is below the floor.  We pay the difference between the ceiling price and the index price only if the index price is above the contracted ceiling price.  No amounts are paid or received if the index price is between the floor and ceiling prices.  For a swap contract, the counterparty is required to make a payment to us if the settlement price for any settlement period is less than the swap price.  We are required to make a payment to the counterparty if the settlement price for the settlement period is greater than the swap price.
	Depending on changes in oil and gas futures markets and management’s view of underlying supply and demand trends, we may increase or decrease our hedging positions.
	We have elected not to account for our derivatives as cash flow hedges.  Therefore, we recognize settlements and changes in the assets or liabilities relating to our open derivative contracts in earnings.  Cash settlements of our contracts are included in cash flows from operating activities in our statements of cash flows.
	The following table summarizes the net gains and (losses) from settlements and changes in fair value of our derivative contracts as presented in our accompanying financial statements.
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands)	2013			2012			2013			2012
	Gain (loss) on derivative instruments, net
	Natural gas contracts	$	376		$	—		$	9,575		$	—
	Oil contracts	(11,200		)	(5,329		)	(8,342		)	661
	Gain (loss) on derivative instruments, net	$	(10,824	)	$	(5,329	)	$	1,233		$	661
	Gains (losses) from settlement of derivative instruments:
	Natural gas contracts	$	1,189		$	—		$	1,189		$	—
	Oil contracts	(7,286		)	—			(5,521		)	—
	Settlement gains (losses)	$	(6,097	)	$	—		$	(4,332	)	$	—
	Our derivative contracts are carried at their fair value on our balance sheet using Level 2 inputs.  We estimate the fair value with internal risk-adjusted discounted cash flow calculations.  Cash flows are based on published forward commodity price curves for the underlying commodity as of the date of the estimate.  For collars, we estimate the option value of the contract floors and ceilings using an option pricing model which takes into account market volatility, market prices, and contract terms.
	The fair value of our derivative instruments in an asset position includes a measure of counterparty credit risk and the fair value of instruments in a liability position includes a measure of our own non-performance risk.  These credit risks are based on current published credit default swap rates.
	Due to the volatility of commodity prices, the estimated fair value of our derivative instruments is subject to fluctuation from period to period, which could result in significant differences between the current estimated fair value and the ultimate settlement price.
	Our derivative instruments are subject to enforceable master netting arrangements, which allow us to offset recognized asset and liability fair value amounts on contracts with the same counterparty.  Our policy is to not offset asset and liability positions in our accompanying balance sheets.
	The following table presents the amounts and classifications of our derivative assets and liabilities as of September 30, 2013, as well as the potential effect of netting arrangements on contracts with the same counterparty.  At December 31, 2012, we had no outstanding derivative contracts.
	September 30, 2013:	Balance Sheet Location		Asset			Liability
	(in thousands)
	Oil contracts	Current assets — Derivative instruments		$	303		$	—
	Natural gas contracts	Current assets — Derivative instruments		$	6,865		$	—
	Oil contracts	Non-current assets — Derivative instruments		$	1,196		$	—
	Natural gas contracts	Non-current assets — Derivative instruments		$	1,521		$	—
	Oil contracts	Current liabilities — Derivative instruments		$	—		$	4,320
	Total gross amounts presented in accompanying balance sheet			$	9,885		$	4,320
	Less: gross amounts not offset in the accompanying balance sheet			$	(3,995	)	$	(3,995	)
	Net amount:			$	5,890		$	325
	We are exposed to financial risks associated with our derivative contracts from non-performance by our counterparties.  We have mitigated our exposure to any single counterparty by contracting with a number of financial institutions, each of which has a high credit rating and is a member of our bank credit facility.  Our member banks do not require us to post collateral for our hedge liability positions.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
Fair Value Measurements	'
Fair Value Measurements	'
	3.              Fair Value Measurements
	Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price).  The Financial Accounting Standards Board (FASB) has established a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value.  This hierarchy consists of three broad levels.  Level 1 inputs are the highest priority and consist of unadjusted quoted prices in active markets for identical assets and liabilities.  Level 2 are inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly.  Level 3 are unobservable inputs for an asset or liability.
	The following tables provide fair value measurement information for certain assets and liabilities as of September 30, 2013 and December 31, 2012:
	September 30, 2013:	Carrying			Fair
	(in thousands)	Amount			Value
	Financial Assets (Liabilities):
	Bank debt	$	(150,000	)	$	(150,000	)
	5.875% Notes due 2022	$	(750,000	)	$	(765,000	)
	Derivative instruments — assets	$	9,885		$	9,885
	Derivative instruments — liabilities	$	(4,320	)	$	(4,320	)
	(in thousands)	Carrying			Fair
	December 31, 2012:	Amount			Value
	Financial (Liabilities):
	5.875% Notes due 2022	$	(750,000	)	$	(825,750	)
	Assessing the significance of a particular input to the fair value measurement requires judgment, including the consideration of factors specific to the asset or liability.  The following methods and assumptions were used to estimate the fair value of the assets and liabilities in the table above.
	Debt (Level 1)
	The fair value of our bank debt at September 30, 2013 was estimated to approximate the carrying amount because the floating rate interest paid on such debt was set for periods of three months or less.
	The fair value for our 5.875% fixed rate notes was based on their last traded value before period end.
	Derivative Instruments (Level 2)
	The fair value of our derivative instruments was estimated using internal discounted cash flow calculations.  Cash flows are based on the stated contract prices and current and published forward commodity price curves, adjusted for volatility.  The cash flows are risk adjusted relative to non-performance for both our counterparties and our liability positions.  Please see Note 2 for further information on the fair value of our derivative instruments.
	Other Financial Instruments
	The carrying amounts of our cash, cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued liabilities approximate fair value because of the short-term maturities and/or liquid nature of these assets and liabilities.
	Most of our accounts receivable balances are uncollateralized and result from transactions with other companies in the oil and gas industry.  Concentration of customers may impact our overall credit risk because our customers may be similarly affected by changes in economic or other conditions within the industry.
	We routinely assess the recoverability of all material accounts receivable to determine their collectability.  We accrue a reserve to the allowance for doubtful accounts when, based on the judgment of management, it is probable that a receivable will not be collected and the amount of the reserve may be reasonably estimated.  At September 30, 2013 and December 31, 2012, the allowance for doubtful accounts was $6.0 and $6.5 million, respectively.

Capital_Stock

Capital Stock	9 Months Ended
	Sep. 30, 2013
Capital Stock	'
Capital Stock	'
	4.              Capital Stock
	Authorized capital stock consists of 200 million shares of common stock and 15 million shares of preferred stock.  At September 30, 2013, there were no shares of preferred stock outstanding.  A summary of our common stock activity for the nine months ended September 30, 2013 follows:
	(in thousands)
	Issued and outstanding as of December 31, 2012	86,596
	Restricted shares issued under compensation plans, net of reacquired stock and cancellations	41
	Option exercises, net of cancellations	201
	Issued and outstanding as of September 30, 2013	86,838
	Dividends
	In September 2013, the Board of Directors declared a cash dividend of $0.14 per share.  The dividend is payable on December 2, 2013 to stockholders of record on November 15, 2013.  Future dividend payments will depend on our level of earnings, financial requirements, and other factors considered relevant by the Board of Directors.

Stockbased_Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2013
Stock-based Compensation	'
Stock-based Compensation	'
	5.              Stock-based Compensation
	Our 2011 Equity Incentive Plan (the 2011 Plan) was approved by stockholders in May 2011 and our previous plan was terminated at that time.  Outstanding awards under the previous plan were not impacted.  The 2011 Plan provides for grants of stock options, restricted stock, restricted stock units, performance stock and performance stock units.  A total of 5.3 million shares of common stock may be issued under the 2011 Plan.
	We have recognized non-cash stock-based compensation cost as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands)	2013			2012			2013			2012
	Restricted stock	$	5,329		$	10,769		$	17,252		$	24,319
	Stock options	940			692			2,355			2,117
		6,269			11,461			19,607			26,436
	Less amounts capitalized to oil and gas properties	(2,922		)	(3,160		)	(9,148		)	(8,917		)
	Compensation expense	$	3,347		$	8,301		$	10,459		$	17,519
	Historical amounts may not be representative of future amounts as additional awards may be granted.
	Restricted Stock and Units
	The following tables provide information about restricted stock awards granted during the three and nine months ended September 30, 2013 and 2012.
		Three Months Ended					Three Months Ended
		September 30, 2013					September 30, 2012
		Number		Weighted			Number		Weighted
		of Shares		Average			of Shares		Average
				Grant-Date					Grant-Date
				Fair Value					Fair Value
	Performance-based stock awards	26,000		$	56.85		24,000		$	48.24
	Service-based stock awards	228,200		$	72.83		238,100		$	53.19
	Total restricted stock awards	254,200		$	71.2		262,100		$	52.73
		Nine Months Ended					Nine Months Ended
		September 30, 2013					September 30, 2012
		Number		Weighted			Number		Weighted
		of Shares		Average			of Shares		Average
				Grant-Date					Grant-Date
				Fair Value					Fair Value
	Performance-based stock awards	26,000		$	56.85		262,770		$	43.22
	Service-based stock awards	277,236		$	72.49		294,198		$	54.03
	Total restricted stock awards	303,236		$	71.15		556,968		$	48.93
	From time to time, performance-based awards are granted to eligible executives and are subject to market condition-based vesting determined by our stock price performance relative to a defined peer group’s stock price performance.  After three years of continued service, an executive will be entitled to vest in 50% to 100% of the award.  In accordance with Internal Revenue Code Section 162(m), certain of the amounts awarded may not be deductible for tax purposes.  Service-based stock awards granted to other eligible employees and non-employee directors have vesting schedules of three to five years.
	Compensation cost for the performance-based stock awards is based on the grant-date fair value of the award utilizing a Monte Carlo simulation model.  Compensation cost for the service-based vesting restricted shares is based upon the grant-date market value of the award.  Such costs are recognized ratably over the applicable vesting period.
	The following table reflects the non-cash compensation cost related to our restricted stock:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands)	2013			2012			2013			2012
	Performance-based stock awards	$	2,710		$	7,719		$	7,963		$	15,390
	Service-based stock awards	2,619			3,050			9,289			8,929
		5,329			10,769			17,252			24,319
	Less amounts capitalized to oil and gas properties	(2,491		)	(2,912		)	(8,229		)	(8,081		)
	Restricted stock compensation expense	$	2,838		$	7,857		$	9,023		$	16,238
	The 2012 compensation cost for the performance-based awards includes $3.9 million of accelerated compensation expense related to the death of our former Chairman, F.H. Merelli.
	Unrecognized compensation cost related to unvested restricted shares at September 30, 2013 was $52.7 million, which we expect to recognize over a weighted average period of approximately 2.5 years.
	The following table provides information on restricted stock and unit activity as of September 30, 2013 and changes during the year.  A restricted unit held by an employee represents a right to an unrestricted share of common stock upon completion of defined vesting and holding periods.  A restricted unit held by a non-employee director represents an election to defer payment of director fees until the time specified by the director in his deferred compensation agreement.  The remaining outstanding restricted units shown below represent restricted units held by a non-employee director who has elected to defer payment of common stock represented by the units until termination of his service on the Board of Directors.
		Restricted		Restricted
		Stock		Units
	Outstanding as of January 1, 2013	1,838,736		33,838
	Vested	(383,175	)	N/A
	Converted to stock	N/A		(25,000	)
	Granted	303,236		—
	Canceled	(133,530	)	—
	Outstanding as of September 30, 2013	1,625,267		8,838
	Vested included in outstanding	N/A		8,838
	Stock Options
	The following table provides information about stock options granted in 2013 and 2012:
		Three and Nine			Three and Nine
		Months Ended			Months Ended
		September 30,			September 30,
		2013			2012
	Options	144,400			152,800
	Weighted average grant-date fair value	$	21.64		$	20.55
Weighted average exercise price	$	72.25		$	51.92
Options granted under our 2011 and previous plans expire seven to ten years from the grant date and have service-based vesting schedules of three to five years.  The plans provide that all grants have an exercise price of the average of the high and low prices of our common stock as reported by the New York Stock Exchange on the date of grant.
Compensation cost related to stock options is based on the grant-date fair value of the award, recognized ratably over the applicable vesting period.  We estimate the fair value using the Black-Scholes option-pricing model.  Expected volatilities are based on the historical volatility of our common stock.  We also use historical data to estimate the probability of option exercise, expected years until exercise and potential forfeitures.  We use U.S. Treasury bond rates in effect at the grant date for our risk-free interest rates.
Non-cash compensation cost related to our stock options is reflected in the following table:
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(in thousands)	2013			2012			2013			2012
Stock option awards	$	940		$	692		$	2,355		$	2,117
Less amounts capitalized to oil and gas properties	(431		)	(248		)	(919		)	(836		)
Stock option compensation expense	$	509		$	444		$	1,436		$	1,281
As of September 30, 2013, there was $5.1 million of unrecognized compensation cost related to non-vested stock options.  We expect to recognize that cost pro rata over a weighted-average period of approximately 2.0 years.
Information about outstanding stock options is summarized below:
	Options		Weighted			Weighted		Aggregate
			Average			Average		Intrinsic
			Exercise			Remaining		Value
			Price			Term		(in thousands)
Outstanding as of January 1, 2013	687,459		$	54.51
Granted	144,400		$	72.25
Exercised	(201,295	)	$	50.51
Canceled	(2,663	)	$	86
Forfeited	(15,443	)	$	65.51
Outstanding as of September 30, 2013	612,458		$	59.59		5.6 Years		$	21,721
Exercisable as of September 30, 2013	262,776		$	53.98		5.1 Years		$	10,796
The following table provides information regarding the options exercised and the grant-date fair value of options vested:
	Nine Months Ended
	September 30,
(dollars in thousands)	2013			2012
Number of options exercised	201,295			505,057
Cash received from option exercises	$	10,168		$	10,410
Intrinsic value of options exercised	$	6,811		$	20,232
Grant-date fair value of options vested	$	2,521		$	2,466
The following summary reflects the status of non-vested stock options as of September 30, 2013 and changes during the year:
	Options		Weighted			Weighted
			Average			Average
			Grant-Date			Exercise
			Fair Value			Price
Non-vested as of January 1, 2013	317,062		$	23.22		$	60.58
Granted	144,400		$	21.64		$	72.25
Vested	(96,337	)	$	26.17		$	65.54
Forfeited	(15,443	)	$	25.96		$	65.51
Non-vested as of September 30, 2013	349,682		$	21.63		$	63.82

Asset_Retirement_Obligations

Asset Retirement Obligations	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligations	'
Asset Retirement Obligations	'
	6.              Asset Retirement Obligations
	We recognize the fair value of liabilities for retirement obligations associated with tangible long-lived assets in the period in which there is a legal obligation associated with the retirement of such assets and the amount can be reasonably estimated.  The associated asset retirement costs are capitalized as part of the carrying amount of the long-lived asset.  This liability includes costs related to the abandonment of wells, the removal of facilities and equipment, and site restorations.  Subsequent to initial measurement, the asset retirement liability is required to be accreted each period.  If the fair value of a recorded asset retirement obligation changes, a revision is recorded to both the asset retirement obligation and the asset retirement capitalized cost.  Capitalized costs are included as a component of the DD&A calculations.
	The following table reflects the components of the change in the carrying amount of the asset retirement obligation for the nine months ended September 30, 2013:
	(in thousands)
	Asset retirement obligation at January 1, 2013	$	185,138
	Liabilities incurred	4,272
	Liability settlements and disposals	(41,540		)
	Accretion expense	5,987
	Revisions of estimated liabilities	2,502
	Asset retirement obligation at September 30, 2013	156,359
	Less current obligation	(49,435		)
	Long-term asset retirement obligation	$	106,924

LongTerm_Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2013
Long-Term Debt	'
Long-Term Debt	'
	7.              Long-Term Debt
	Debt at September 30, 2013 and December 31, 2012 consisted of the following:
	(in thousands)	September 30,		December 31,
		2013		2012
	Bank debt	$	150,000	$	—
	5.875% Senior Notes due 2022	750,000		750,000
	Total long-term debt	$	900,000	$	750,000
	Bank Debt
	We have a five-year senior unsecured revolving credit facility (Credit Facility), which matures July 14, 2016.  The Credit Facility provides for a borrowing base of $2.25 billion with aggregate commitments of $1 billion from our lenders.  The borrowing base under the Credit Facility is determined at the discretion of the lenders based on the value of our proved reserves.  The next regular annual redetermination date is scheduled for April 15, 2014.
	As of September 30, 2013, we had $150 million of bank debt outstanding at a weighted average interest rate of 2.28%.  We also had letters of credit outstanding under the Credit Facility of $2.5 million, leaving an unused borrowing availability of $847.5 million.
	At our option, borrowings under the Credit Facility may bear interest at either (a) LIBOR plus 1.75-2.5%, based on our leverage ratio, or (b) the higher of (i) a prime rate, (ii) the federal funds effective rate plus 0.50%, or (iii) adjusted one-month LIBOR plus 1.0% plus, in each case, an additional 0.75-1.5%, based on our leverage ratio.
	The Credit Facility also has financial covenants that include the maintenance of current assets (including unused bank commitments) to current liabilities of greater than 1.0 to 1.0.  We also must maintain a leverage ratio of total debt to earnings before interest expense, income taxes and non-cash items (such as depreciation, depletion and amortization expense, unrealized gains and losses on commodity derivatives, ceiling test write-downs, and goodwill impairments) of not more than 3.5 to 1.0.  Other covenants could limit our ability to incur additional indebtedness, pay dividends, repurchase our common stock, or sell assets.  As of September 30, 2013, we were in compliance with all of the financial and non-financial covenants.
	5.875% Notes due 2022
	In April 2012, we issued $750 million of 5.875% senior notes due May 1, 2022, with interest payable semiannually in May and November.  The notes were sold to the public at par.  The notes are governed by an indenture containing certain covenants, events of default and other restrictive provisions.  We may redeem the notes in whole or in part, at any time on or after May 1, 2017, at redemption prices of 102.938% of the principal amount as of May 1, 2017, declining to 100% on May 1, 2020 and thereafter.
	7.125% Notes due 2017
	In May 2007, we issued $350 million of 7.125% senior unsecured notes at par that were scheduled to mature May 1, 2017.  On March 22, 2012, we commenced a cash tender offer (Tender Offer) to purchase all of the outstanding 7.125% senior notes.  The Tender Offer was completed in the second quarter of 2012.  We recognized a $16.2 million loss on early extinguishment of debt during the second quarter of 2012.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Taxes	'
Income Taxes	'
	8.              Income Taxes
	The components of our provision for income taxes are as follows:
		Three Months Ended					Nine Months Ended
		September 30,					September 30,
	(in thousands)	2013		2012			2013		2012
	Current benefit	$	—	$	(1,629	)	$	—	$	(1,629	)
	Deferred taxes	81,823		49,568			211,615		150,648
		$	81,823	$	47,939		$	211,615	$	149,019
	At December 31, 2012, we had a U.S. net tax operating loss carryforward of approximately $480.7 million, which would expire between 2031 and 2032.  We believe that the carryforward will be utilized before it expires.  We also had an alternative minimum tax credit carryforward of approximately $4.4 million.
	At September 30, 2013, we had no unrecognized tax benefits that would impact our effective rate and we have made no provisions for interest or penalties related to uncertain tax positions.  The tax years 2009-2012 remain open to examination by the Internal Revenue Service of the United States.  We file tax returns with various state taxing authorities, which remain open to examination for the 2008-2012 tax years.
	Our provision for income taxes differed from the U.S. statutory rate of 35% primarily due to state income taxes and non-deductible expenses. The effective income tax rates for the nine months ended September 30, 2013 and September 30, 2012 were 37.2% and 36.9%, respectively.

Supplemental_Disclosure_of_Cas

Supplemental Disclosure of Cash Flow Information:	9 Months Ended
	Sep. 30, 2013
Supplemental Disclosure of Cash Flow Information:	'
Supplemental Disclosure of Cash Flow Information:	'
	9. Supplemental Disclosure of Cash Flow Information:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(in thousands)	2013		2012		2013		2012
	Cash paid during the period for:
	Interest expense (including capitalized amounts)	$	1,932	$	1,017	$	27,158	$	15,374
	Interest capitalized	$	394	$	432	$	15,706	$	11,304
	Income taxes	$	—	$	—	$	205	$	375
	Cash received for income taxes	$	213	$	57	$	450	$	49,293

Earnings_per_Share

Earnings per Share	9 Months Ended
	Sep. 30, 2013
Earnings per Share	'
Earnings per Share	'
	10.       Earnings per Share
	The calculations of basic and diluted net earnings per common share under the two-class method are presented below:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands, except per share data)	2013			2012			2013			2012
	Basic:
	Net income	$	138,370		$	84,262		$	357,862		$	254,671
	Participating securities’ share in earnings	(2,375		)	(1,628		)	(6,049		)	(4,929		)
	Net income applicable to common shareholders	$	135,995		$	82,634		$	351,813		$	249,742
	Diluted:
	Net income	$	138,370		$	84,262		$	357,862		$	254,671
	Participating securities’ share in earnings	(2,371		)	(1,622		)	(6,041		)	(4,910		)
	Net income applicable to common shareholders	$	135,999		$	82,640		$	351,821		$	249,761
	Shares:
	Basic shares outstanding	85,213			84,681			85,213			84,681
	Incremental shares from assumed exercise of stock options	134			316			117			340
	Fully diluted common stock	85,347			84,997			85,330			85,021
	Excluded (1)	232			400			254			408
	Earnings per share to common shareholders: (2)
	Basic	$	1.59		$	0.97		$	4.12		$	2.94
	Diluted	$	1.59		$	0.97		$	4.12		$	2.93
	(1)         Inclusion of certain outstanding stock options would have an anti-dilutive effect.
	(2)         Earnings per share are based on actual figures rather than the rounded figures presented.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies	'
Commitments and Contingencies	'
	11.       Commitments and Contingencies
	Commitments
	We have commitments of $176.9 million to finish drilling and completing wells in progress at September 30, 2013.
	In New Mexico and Texas, we are constructing gathering facilities and pipelines.  At September 30, 2013, we had commitments of $4.1 million relating to these construction projects.
	At September 30, 2013, we had firm sales contracts to deliver approximately 25 Bcf of natural gas over the next 11 months.  If this gas is not delivered, our financial commitment would be approximately $82.8 million.  This commitment will fluctuate due to price volatility and actual volumes delivered.  However, we believe no financial commitment will be due based on our current proved reserves and production levels.
	We have other various transportation and delivery commitments in the normal course of business, which approximate $3.5 million over the next four years.
	We have various commitments for office space and equipment under operating lease arrangements totaling $130.7 million for the next five years and beyond.
	All of the noted commitments were routine and were made in the normal course of our business.
	Litigation
	In the normal course of business, we have various litigation matters.  We assess the probability of estimable amounts related to litigation matters in accordance with guidance established by the FASB and adjust our accruals accordingly.  Though some of the related claims may be significant, we believe the resolution of them, individually or in the aggregate, would not have a material adverse effect on our financial condition or results of operations after consideration of current accruals.
	Hitch Enterprises, Inc. et al. v. Cimarex Energy Co. et al.
	On December 11, 2012, Cimarex entered into a preliminary resolution of the Hitch Enterprises, Inc., et al. v. Cimarex Energy Co., et al. (Hitch) litigation matter for $16.4 million.  Hitch is a statewide royalty class action pending in the Federal District Court in Oklahoma City, Oklahoma.  The settlement was reached at a mediation, which occurred after the parties began to exchange information, including damage analyses, on November 16, 2012.  On July 2, 2013, the Court entered a judgment approving the parties’ settlement.  The judgment became final and unappealable on August 2, 2013. Cimarex distributed the settlement proceeds pursuant to the Court’s order in September 2013 and the administration of the settlement is ongoing.  In the fourth quarter of 2012, we accrued $16.4 million for this matter.
	H.B. Krug, et al versus H&P
	In January 2009, the Tulsa County District Court issued a judgment totaling $119.6 million in the H.B. Krug, et al. v. Helmerich & Payne, Inc. (H&P) case.  This lawsuit originally was filed in 1998 and addressed H&P’s conduct pertaining to a 1989 take-or-pay settlement, along with potential drainage and other related issues.  Pursuant to the 2002 spin-off transaction to shareholders of H&P, by which Cimarex became a publicly-traded entity, Cimarex assumed the assets and liabilities of H&P’s exploration and production business, including this lawsuit.  In 2008, we recorded a litigation expense of $119.6 million for this lawsuit.  We have accrued additional post-judgment interest and costs during the appeal of the District Court’s judgment.
	On August 18, 2011, the Oklahoma Court of Appeals reversed and remanded the $112.7 million disgorgement of profits award, holding the District Court erred in failing to make the required findings of fact and conclusions of law.  In all other respects, the Court of Appeals affirmed the District Court’s judgment, including damages of $6.845 million.  On February 13, 2012, the Oklahoma Supreme Court granted Cimarex’s Petition for Certiorari, which requested a review of the affirmed portion of the judgment.  We are awaiting a ruling from the Oklahoma Supreme Court, and the final outcome cannot be determined at this time.  If the District Court’s original judgment is ultimately affirmed in its entirety, the $119.6 million, plus the then-determined amount of post-judgment interest and costs would become payable.
	The following table reflects the change in the non-current accrued liability for this lawsuit for the nine months ended September 30, 2013:
	(in thousands)
	Outstanding at January 1, 2013	$	155,374
	Accrued post-judgment interest and costs	7,070
	Outstanding at September 30, 2013	$	162,444

Property_Sales_and_Acquisition

Property Sales and Acquisitions	9 Months Ended
	Sep. 30, 2013
Property Sales and Acquisitions	'
Property Sales and Acquisitions	'
	12.               Property Salesand Acquisitions
	We sold interests in various oil and gas properties for $37.7 million during the first nine months of 2013. There were $12.2 million of oil and gas property sales during the first nine months of 2012. During the second quarter of 2013, we also sold a 50% interest in our Culberson County, Texas Triple Crown gas gathering and processing system for approximately $31 million.
	During the first nine months of 2013 and 2012, we had property acquisitions of $6.2 million and $11.3 million, respectively.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2013
Basis of Presentation	'
Restricted Cash	'
	Restricted Cash
	At December 31, 2012, we had restricted cash of $811 thousand included in our non-current other assets which consisted of monies from third parties that were being held by Cimarex, as operator of a property in Oklahoma, until the ownership disputes among the third parties could be resolved.  As of September 30, 2013, the ownership disputes have been resolved and we have transferred the restricted cash and the related liability from non-current to current.
Oil and Gas Properties	'
	Oil and Gas Properties
	We use the full cost method of accounting for our oil and gas operations.  Accounting rules require us to perform a quarterly “ceiling test” calculation to test our oil and gas properties for possible impairment.  The primary components impacting this calculation are commodity prices, reserve quantities added and produced, overall exploration and development costs, depletion expense, and tax effects.  If the net capitalized cost of our oil and gas properties subject to amortization (the carrying value) exceeds the ceiling limitation, the excess would be charged to expense.  The ceiling limitation is equal to the sum of the present value discounted at 10% of estimated future net cash flows from proved reserves, the cost of properties not being amortized, the lower of cost or estimated fair value of unproven properties included in the costs being amortized, and all related tax effects.
	At September 30, 2013, the calculated value of the ceiling limitation exceeded the carrying value of our oil and gas properties subject to the test, and no impairment was necessary.  Our ceiling limitation has improved since December 31, 2012.  However, a decline of 5% in the value of the ceiling limitation would have resulted in an impairment.  If pricing conditions decline, or if there is a negative impact on one or more of the other components of the calculation, we may incur a full cost ceiling impairment related to our oil and gas properties in future quarters.
Use of Estimates	'
	Use of Estimates
	The more significant areas requiring the use of management’s estimates and judgments relate to the estimation of proved oil and gas reserves, the use of these oil and gas reserves in calculating depletion, depreciation, and amortization (DD&A), the use of the estimates of future net revenues in computing ceiling test limitations and estimates of future abandonment obligations used in recording asset retirement obligations, and the assessment of goodwill.  Estimates and judgments are also required in determining allowance for bad debt, impairments of undeveloped properties and other assets, purchase price allocation, valuation of deferred tax assets, fair value measurements, and commitments and contingencies.
Recently Issued Accounting Standards	'
	Recently Issued Accounting Standards
	No significant accounting standards applicable to Cimarex have been issued during the quarter ended September 30, 2013.

Basis_of_Presentation_Tables

Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2013
Basis of Presentation	'
Schedule of components of receivable accounts, accounts payable, and accrued liabilities	'
	(in thousands)	September 30,		December 31,
		2013		2012
	Receivables, net of allowance
	Trade	$	87,069	$	55,528
	Oil and gas sales	289,673		239,106
	Gas gathering, processing, and marketing	14,363		7,901
	Other	—		439
	Receivables, net	$	391,105	$	302,974
	Accounts payable
	Trade	$	84,152	$	88,168
	Gas gathering, processing, and marketing	26,930		15,485
	Accounts payable	$	111,082	$	103,653
	Accrued liabilities
	Exploration and development	$	173,066	$	155,002
	Taxes other than income	29,022		29,179
	Other	201,325		208,728
	Accrued liabilities	$	403,413	$	392,909

Derivative_InstrumentsHedging_

Derivative Instruments/Hedging (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative	'
Net gains and (losses) from settlements and changes in fair value of derivative contracts	'
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands)	2013			2012			2013			2012
	Gain (loss) on derivative instruments, net
	Natural gas contracts	$	376		$	—		$	9,575		$	—
	Oil contracts	(11,200		)	(5,329		)	(8,342		)	661
	Gain (loss) on derivative instruments, net	$	(10,824	)	$	(5,329	)	$	1,233		$	661
	Gains (losses) from settlement of derivative instruments:
	Natural gas contracts	$	1,189		$	—		$	1,189		$	—
	Oil contracts	(7,286		)	—			(5,521		)	—
	Settlement gains (losses)	$	(6,097	)	$	—		$	(4,332	)	$	—
Schedule of amounts and classifications of entity's derivative assets and liabilities as well as the potential effect of netting arrangements on contracts with the same counterparty	'
	September 30, 2013:	Balance Sheet Location		Asset			Liability
	(in thousands)
	Oil contracts	Current assets — Derivative instruments		$	303		$	—
	Natural gas contracts	Current assets — Derivative instruments		$	6,865		$	—
	Oil contracts	Non-current assets — Derivative instruments		$	1,196		$	—
	Natural gas contracts	Non-current assets — Derivative instruments		$	1,521		$	—
	Oil contracts	Current liabilities — Derivative instruments		$	—		$	4,320
	Total gross amounts presented in accompanying balance sheet			$	9,885		$	4,320
	Less: gross amounts not offset in the accompanying balance sheet			$	(3,995	)	$	(3,995	)
	Net amount:			$	5,890		$	325
Oil contracts	'
Derivative	'
Outstanding hedging contracts relative to future production	'
								Weighted Average Price							Fair Value
	Period	Type		Volume/Day		Index(1)		Floor			Ceiling		Swap		(in thousands)
	Oct 13 – Dec 13	Collars		6,000 Bbls		WTI		$	85		$	102.31	N/A		$	(1,311	)
	Oct 13 – Dec 13	Swaps		6,000 Bbls		WTI		N/A			N/A		$	96.13	$	(2,987	)
	Jan 14 – Dec 14	Collars		6,000 Bbls		WTI		$	85		$	105.68	N/A		$	1,477
	(1)         WTI refers to West Texas Intermediate price as quoted on the New York Mercantile Exchange.
Gas Contracts	'
Derivative	'
Outstanding hedging contracts relative to future production	'
								Weighted Average					Fair Value
								Price
	Period	Type		Volume/Day		Index(1)		Floor			Ceiling		(in thousands)
	Oct 13 – Dec 14	Collars		80,000 MMBtu		PEPL		$	3.51		$	4.57	$	8,386
	(1)                PEPL refers to Panhandle Eastern Pipe Line, Tex/OK Mid-Continent Index as quoted in Platt’s Inside FERC.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Measurements	'
Fair value measurement information for certain assets and liabilities	'
	September 30, 2013:	Carrying			Fair
	(in thousands)	Amount			Value
	Financial Assets (Liabilities):
	Bank debt	$	(150,000	)	$	(150,000	)
	5.875% Notes due 2022	$	(750,000	)	$	(765,000	)
	Derivative instruments — assets	$	9,885		$	9,885
	Derivative instruments — liabilities	$	(4,320	)	$	(4,320	)
	(in thousands)	Carrying			Fair
	December 31, 2012:	Amount			Value
	Financial (Liabilities):
	5.875% Notes due 2022	$	(750,000	)	$	(825,750	)

Capital_Stock_Tables

Capital Stock (Tables)	9 Months Ended
	Sep. 30, 2013
Capital Stock	'
Common stock activity	'
	(in thousands)
	Issued and outstanding as of December 31, 2012	86,596
	Restricted shares issued under compensation plans, net of reacquired stock and cancellations	41
	Option exercises, net of cancellations	201
	Issued and outstanding as of September 30, 2013	86,838

Stockbased_Compensation_Tables

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2013
Options, Restricted Stock and Unit Awards	'
Recognition of non-cash stock-based compensation cost	'
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands)	2013			2012			2013			2012
	Restricted stock	$	5,329		$	10,769		$	17,252		$	24,319
	Stock options	940			692			2,355			2,117
		6,269			11,461			19,607			26,436
	Less amounts capitalized to oil and gas properties	(2,922		)	(3,160		)	(9,148		)	(8,917		)
	Compensation expense	$	3,347		$	8,301		$	10,459		$	17,519
Restricted Stock and Units	'
Options, Restricted Stock and Unit Awards	'
Recognition of non-cash stock-based compensation cost	'
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands)	2013			2012			2013			2012
	Performance-based stock awards	$	2,710		$	7,719		$	7,963		$	15,390
	Service-based stock awards	2,619			3,050			9,289			8,929
		5,329			10,769			17,252			24,319
	Less amounts capitalized to oil and gas properties	(2,491		)	(2,912		)	(8,229		)	(8,081		)
	Restricted stock compensation expense	$	2,838		$	7,857		$	9,023		$	16,238
Summary of restricted stock awards granted	'
		Three Months Ended					Three Months Ended
		September 30, 2013					September 30, 2012
		Number		Weighted			Number		Weighted
		of Shares		Average			of Shares		Average
				Grant-Date					Grant-Date
				Fair Value					Fair Value
	Performance-based stock awards	26,000		$	56.85		24,000		$	48.24
	Service-based stock awards	228,200		$	72.83		238,100		$	53.19
	Total restricted stock awards	254,200		$	71.2		262,100		$	52.73
		Nine Months Ended					Nine Months Ended
		September 30, 2013					September 30, 2012
		Number		Weighted			Number		Weighted
		of Shares		Average			of Shares		Average
				Grant-Date					Grant-Date
				Fair Value					Fair Value
	Performance-based stock awards	26,000		$	56.85		262,770		$	43.22
	Service-based stock awards	277,236		$	72.49		294,198		$	54.03
	Total restricted stock awards	303,236		$	71.15		556,968		$	48.93
Restricted stock and unit activity	'
		Restricted		Restricted
		Stock		Units
	Outstanding as of January 1, 2013	1,838,736		33,838
	Vested	(383,175	)	N/A
	Converted to stock	N/A		(25,000	)
	Granted	303,236		—
	Canceled	(133,530	)	—
	Outstanding as of September 30, 2013	1,625,267		8,838
	Vested included in outstanding	N/A		8,838
Options	'
Options, Restricted Stock and Unit Awards	'
Recognition of non-cash stock-based compensation cost	'
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands)	2013			2012			2013			2012
	Stock option awards	$	940		$	692		$	2,355		$	2,117
	Less amounts capitalized to oil and gas properties	(431		)	(248		)	(919		)	(836		)
	Stock option compensation expense	$	509		$	444		$	1,436		$	1,281
Summary of stock options granted	'
		Three and Nine			Three and Nine
		Months Ended			Months Ended
		September 30,			September 30,
		2013			2012
	Options	144,400			152,800
	Weighted average grant-date fair value	$	21.64		$	20.55
	Weighted average exercise price	$	72.25		$	51.92
Outstanding stock options	'
		Options		Weighted			Weighted		Aggregate
				Average			Average		Intrinsic
				Exercise			Remaining		Value
				Price			Term		(in thousands)
	Outstanding as of January 1, 2013	687,459		$	54.51
	Granted	144,400		$	72.25
	Exercised	(201,295	)	$	50.51
	Canceled	(2,663	)	$	86
	Forfeited	(15,443	)	$	65.51
	Outstanding as of September 30, 2013	612,458		$	59.59		5.6 Years		$	21,721
	Exercisable as of September 30, 2013	262,776		$	53.98		5.1 Years		$	10,796
Summary of information regarding options exercised and grant-date fair value of options vested	'
		Nine Months Ended
		September 30,
	(dollars in thousands)	2013			2012
	Number of options exercised	201,295			505,057
	Cash received from option exercises	$	10,168		$	10,410
	Intrinsic value of options exercised	$	6,811		$	20,232
	Grant-date fair value of options vested	$	2,521		$	2,466
Status of non-vested stock options	'
		Options		Weighted			Weighted
				Average			Average
				Grant-Date			Exercise
				Fair Value			Price
	Non-vested as of January 1, 2013	317,062		$	23.22		$	60.58
	Granted	144,400		$	21.64		$	72.25
	Vested	(96,337	)	$	26.17		$	65.54
	Forfeited	(15,443	)	$	25.96		$	65.51
	Non-vested as of September 30, 2013	349,682		$	21.63		$	63.82

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligations	'
Change in the carrying amount of the asset retirement obligation	'
	(in thousands)
	Asset retirement obligation at January 1, 2013	$	185,138
	Liabilities incurred	4,272
	Liability settlements and disposals	(41,540		)
	Accretion expense	5,987
	Revisions of estimated liabilities	2,502
	Asset retirement obligation at September 30, 2013	156,359
	Less current obligation	(49,435		)
	Long-term asset retirement obligation	$	106,924

LongTerm_Debt_Tables

Long-Term Debt (Tables)	9 Months Ended
	Sep. 30, 2013
Long-Term Debt	'
Summary of debt	'
	(in thousands)	September 30,		December 31,
		2013		2012
	Bank debt	$	150,000	$	—
	5.875% Senior Notes due 2022	750,000		750,000
	Total long-term debt	$	900,000	$	750,000

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2013
Income Taxes	'
Components of the provision for income taxes	'
		Three Months Ended					Nine Months Ended
		September 30,					September 30,
	(in thousands)	2013		2012			2013		2012
	Current benefit	$	—	$	(1,629	)	$	—	$	(1,629	)
	Deferred taxes	81,823		49,568			211,615		150,648
		$	81,823	$	47,939		$	211,615	$	149,019

Supplemental_Disclosure_of_Cas1

Supplemental Disclosure of Cash Flow Information: (Tables)	9 Months Ended
	Sep. 30, 2013
Supplemental Disclosure of Cash Flow Information:	'
Supplemental Disclosure of Cash Flow Information	'
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(in thousands)	2013		2012		2013		2012
	Cash paid during the period for:
	Interest expense (including capitalized amounts)	$	1,932	$	1,017	$	27,158	$	15,374
	Interest capitalized	$	394	$	432	$	15,706	$	11,304
	Income taxes	$	—	$	—	$	205	$	375
	Cash received for income taxes	$	213	$	57	$	450	$	49,293

Earnings_per_Share_Tables

Earnings per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings per Share	'
Calculations of basic and diluted net earnings (loss) per common share under the two-class method	'
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(in thousands, except per share data)	2013			2012			2013			2012
	Basic:
	Net income	$	138,370		$	84,262		$	357,862		$	254,671
	Participating securities’ share in earnings	(2,375		)	(1,628		)	(6,049		)	(4,929		)
	Net income applicable to common shareholders	$	135,995		$	82,634		$	351,813		$	249,742
	Diluted:
	Net income	$	138,370		$	84,262		$	357,862		$	254,671
	Participating securities’ share in earnings	(2,371		)	(1,622		)	(6,041		)	(4,910		)
	Net income applicable to common shareholders	$	135,999		$	82,640		$	351,821		$	249,761
	Shares:
	Basic shares outstanding	85,213			84,681			85,213			84,681
	Incremental shares from assumed exercise of stock options	134			316			117			340
	Fully diluted common stock	85,347			84,997			85,330			85,021
	Excluded (1)	232			400			254			408
	Earnings per share to common shareholders: (2)
	Basic	$	1.59		$	0.97		$	4.12		$	2.94
	Diluted	$	1.59		$	0.97		$	4.12		$	2.93
	(1)         Inclusion of certain outstanding stock options would have an anti-dilutive effect.
	(2)         Earnings per share are based on actual figures rather than the rounded figures presented.

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies	'
Change in the non-current accrued liability for lawsuit	'
	(in thousands)
	Outstanding at January 1, 2013	$	155,374
	Accrued post-judgment interest and costs	7,070
	Outstanding at September 30, 2013	$	162,444

Basis_of_Presentation_Details

Basis of Presentation (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Restricted Cash	'	'
Non-current restricted cash	'	$811
Oil and Gas Properties	'	'
Discount rate for calculating present value of estimated future net revenues from proved reserves (as a percent)	10.00%	'
Impairment of oil and gas properties	0	'
Ceiling limitation used in ceiling test sensitivity analysis	5.00%	'
Receivables, net of allowance	'	'
Trade	87,069	55,528
Oil and gas sales	289,673	239,106
Gas gathering, processing, and marketing	14,363	7,901
Other	'	439
Receivables, net	391,105	302,974
Accounts payable	'	'
Trade	84,152	88,168
Gas gathering, processing, and marketing	26,930	15,485
Accounts payable	111,082	103,653
Accrued liabilities	'	'
Exploration and development	173,066	155,002
Taxes other than income	29,022	29,179
Other	201,325	208,728
Accrued liabilities	$403,413	$392,909

Derivative_InstrumentsHedging_1

Derivative Instruments/Hedging (Details) (USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Oil Contracts, Collar, WTI Index (in Bbls) | Period from October 2013 to December 2013	'
Fair values of derivative assets and liabilities	'
Volume/Day	6
Fair value	($1,311)
Weighted Average Price	'
Floor, weighted average price	85
Ceiling, weighted average price	102.31
Oil Contracts, Collar, WTI Index (in Bbls) | Period from January 2014 to December 2014	'
Fair values of derivative assets and liabilities	'
Volume/Day	6
Fair value	1,477
Weighted Average Price	'
Floor, weighted average price	85
Ceiling, weighted average price	105.68
Oil Contracts, Swap, WTI Index (in Bbls)	'
Fair values of derivative assets and liabilities	'
Volume/Day	6
Fair value	-2,987
Weighted Average Price	'
Swap, weighted average price	96.13
Gas Contracts, Collar, PEPL Index (in MMBtu)	'
Fair values of derivative assets and liabilities	'
Volume/Day	80
Fair value	$8,386
Weighted Average Price	'
Floor, weighted average price	3.51
Ceiling, weighted average price	4.57

Derivative_InstrumentsHedging_2

Derivative Instruments/Hedging (Details 2) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Gain (loss) on derivative instruments, net	'	'	'	'
Gain (loss) on derivative instruments, net	($10,824)	($5,329)	$1,233	$661
Gains (losses) from settlement of derivative instruments:	'	'	'	'
Settlement gains (losses)	'	'	4,332	'
Derivatives not designated as hedging instruments	'	'	'	'
Gain (loss) on derivative instruments, net	'	'	'	'
Gain (loss) on derivative instruments, net	-10,824	-5,329	1,233	661
Gains (losses) from settlement of derivative instruments:	'	'	'	'
Settlement gains (losses)	-6,097	'	-4,332	'
Natural gas contracts | Derivatives not designated as hedging instruments	'	'	'	'
Gain (loss) on derivative instruments, net	'	'	'	'
Gain (loss) on derivative instruments, net	376	'	9,575	'
Gains (losses) from settlement of derivative instruments:	'	'	'	'
Settlement gains (losses)	1,189	'	1,189	'
Oil contracts | Derivatives not designated as hedging instruments	'	'	'	'
Gain (loss) on derivative instruments, net	'	'	'	'
Gain (loss) on derivative instruments, net	-11,200	-5,329	-8,342	661
Gains (losses) from settlement of derivative instruments:	'	'	'	'
Settlement gains (losses)	($7,286)	'	($5,521)	'

Derivative_InstrumentsHedging_3

Derivative Instruments/Hedging (Details 3) (Derivatives not designated as hedging instruments, USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Asset	'
Total gross amounts presented in accompanying balance sheet	$9,885
Less: gross amounts not offset in the accompanying balance sheet	-3,995
Net amount:	5,890
Liability	'
Total gross amounts presented in accompanying balance sheet	4,320
Less: gross amounts not offset in the accompanying balance sheet	-3,995
Net amount:	325
Oil contracts | Current assets	'
Asset	'
Total gross amounts presented in accompanying balance sheet	303
Oil contracts | Non-current assets	'
Asset	'
Total gross amounts presented in accompanying balance sheet	1,196
Oil contracts | Current liabilities	'
Liability	'
Total gross amounts presented in accompanying balance sheet	4,320
Natural gas contracts | Current assets	'
Asset	'
Total gross amounts presented in accompanying balance sheet	6,865
Natural gas contracts | Non-current assets	'
Asset	'
Total gross amounts presented in accompanying balance sheet	$1,521

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Apr. 30, 2012
In Thousands, unless otherwise specified
5.875% Notes due 2022	'	'	'
Financial Assets (Liabilities):	'	'	'
Interest rate (as a percent)	5.88%	5.88%	5.88%
5.875% Notes due 2022 | Level 1	'	'	'
Financial Assets (Liabilities):	'	'	'
Interest rate (as a percent)	5.88%	5.88%	'
Carrying Amount	'	'	'
Financial Assets (Liabilities):	'	'	'
Derivative instruments - assets	9,885	'	'
Derivative instruments - liabilities	-4,320	'	'
Carrying Amount | 5.875% Notes due 2022	'	'	'
Financial Assets (Liabilities):	'	'	'
Long-term debt	-750,000	-750,000	'
Carrying Amount | Bank debt	'	'	'
Financial Assets (Liabilities):	'	'	'
Long-term debt	-150,000	'	'
Fair Value	'	'	'
Financial Assets (Liabilities):	'	'	'
Derivative instruments - assets	9,885	'	'
Derivative instruments - liabilities	-4,320	'	'
Fair Value | 5.875% Notes due 2022	'	'	'
Financial Assets (Liabilities):	'	'	'
Long-term debt	-765,000	-825,750	'
Fair Value | Bank debt	'	'	'
Financial Assets (Liabilities):	'	'	'
Long-term debt	-150,000	'	'

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (Accounts Receivable, Trade, USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Accounts Receivable, Trade	'	'
Other Financial Instruments	'	'
Aggregate allowance for doubtful accounts	$6	$6.50

Capital_Stock_Details

Capital Stock (Details) (USD $)	1 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Capital Stock	'	'	'
Common stock, shares authorized	200,000,000	200,000,000	200,000,000
Preferred stock, shares authorized	15,000,000	15,000,000	15,000,000
Preferred stock outstanding (in shares)	0	0	'
Summary of issued and outstanding common stock activity	'	'	'
Beginning balance, shares	'	86,595,976	'
Restricted shares issued under compensation plans, net of reacquired stock and cancellations	'	41,000	'
Option exercises, net of cancellations	'	201,000	'
Ending balance, shares	86,838,423	86,838,423	'
Dividends	'	'	'
Cash dividend declared (in dollars per share)	$0.14	'	'

Stockbased_Compensation_Detail

Stock-based Compensation (Details) (USD $)

3 Months Ended

9 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

31-May-11

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Restricted Stock and Units

Restricted Stock

Restricted Stock

Restricted Stock

Restricted Stock

Performance-based stock awards

Performance-based stock awards

Performance-based stock awards

Performance-based stock awards

Performance-based stock awards

Performance-based stock awards

Performance-based stock awards

Service-based stock awards

Service-based stock awards

Service-based stock awards

Service-based stock awards

Service-based stock awards

Service-based stock awards

Options

Options

Options

Options

Options

Options

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Stock-based Compensation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum number of shares of common stock that may be issued under the 2011 Stock Incentive Plan

'

'

'

'

5,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Options, Restricted Stock and Unit Awards

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Compensation expense before capitalized cost

$6,269,000

$11,461,000

$19,607,000

$26,436,000

'

'

$5,329,000

$10,769,000

$17,252,000

$24,319,000

$2,710,000

$7,719,000

$7,963,000

$15,390,000

'

'

'

$2,619,000

$3,050,000

$9,289,000

$8,929,000

'

'

$940,000

$692,000

$2,355,000

$2,117,000

'

'

Less amounts capitalized to oil and gas properties

-2,922,000

-3,160,000

-9,148,000

-8,917,000

'

'

-2,491,000

-2,912,000

-8,229,000

-8,081,000

'

'

'

'

'

'

'

'

'

'

'

'

'

-431,000

-248,000

-919,000

-836,000

'

'

Compensation expense

3,347,000

8,301,000

10,459,000

17,519,000

'

'

2,838,000

7,857,000

9,023,000

16,238,000

'

'

'

'

'

'

'

'

'

'

'

'

'

509,000

444,000

1,436,000

1,281,000

'

'

Restricted stock and units granted (in shares)

'

'

'

'

'

'

254,200

262,100

303,236

556,968

26,000

24,000

26,000

262,770

'

'

'

228,200

238,100

277,236

294,198

'

'

'

'

'

'

'

'

Restricted stock and units granted, weighted average grant-date fair value (in dollars per share)

'

'

'

'

'

'

$71.20

$52.73

$71.15

$48.93

$56.85

$48.24

$56.85

$43.22

'

'

'

$72.83

$53.19

$72.49

$54.03

'

'

'

'

'

'

'

'

Minimum years of continued service before restricted shares issued to certain executives vest

'

'

'

'

'

'

'

'

'

'

'

'

'3 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Award vesting percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

Accelerated compensation cost

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unrecognized compensation costs related to unvested awards (in dollars)

'

'

'

'

'

$52,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$5,100,000

'

$5,100,000

'

'

'

Expected period to recognize unamortized compensation costs related to unvested awards

'

'

'

'

'

'2 years 6 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'2 years

'

'

'

Vesting period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'5 years

'3 years

'

'

'

'

'5 years

'3 years

Stockbased_Compensation_Detail1

Stock-based Compensation (Details 2)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Restricted Stock	'	'	'	'
Restricted stock and unit activity	'	'	'	'
Outstanding at the beginning of the period (in shares)	'	'	1,838,736	'
Vested (in shares)	'	'	-383,175	'
Granted (in shares)	254,200	262,100	303,236	556,968
Canceled (in shares)	'	'	-133,530	'
Outstanding at the end of the period (in shares)	1,625,267	'	1,625,267	'
Restricted Stock Units	'	'	'	'
Restricted stock and unit activity	'	'	'	'
Outstanding at the beginning of the period (in shares)	'	'	33,838	'
Converted to Stock (in shares)	'	'	-25,000	'
Outstanding at the end of the period (in shares)	8,838	'	8,838	'
Vested included in outstanding (in shares)	8,838	'	8,838	'

Stockbased_Compensation_Detail2

Stock-based Compensation (Details 3) (Options, USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Outstanding Stock Options	'	'	'	'
Outstanding balance at beginning of period (in shares)	'	'	687,459	'
Granted (in shares)	144,400	152,800	144,400	152,800
Exercised (in shares)	'	'	-201,295	-505,057
Canceled (in shares)	'	'	-2,663	'
Forfeited (in shares)	'	'	-15,443	'
Outstanding balance at end of period (in shares)	612,458	'	612,458	'
Exercisable at end of period (in shares)	262,776	'	262,776	'
Weighted Average Exercise Price	'	'	'	'
Outstanding balance at beginning of period (in dollars per share)	'	'	$54.51	'
Granted (in dollars per share)	$72.25	$51.92	$72.25	$51.92
Exercised (in dollars per share)	'	'	$50.51	'
Canceled (in dollars per share)	'	'	$86	'
Forfeited (in dollars per share)	'	'	$65.51	'
Outstanding at end of period (in dollars per share)	$59.59	'	$59.59	'
Exercisable at end of period (in dollars per share)	$53.98	'	$53.98	'
Weighted Average Remaining Term	'	'	'	'
Weighted Average Remaining Term, Outstanding at end of period	'	'	'5 years 7 months 6 days	'
Weighted Average Remaining Term, Exercisable at end of period	'	'	'5 years 1 month 6 days	'
Aggregate Intrinsic Value	'	'	'	'
Aggregate Intrinsic Value Outstanding at end of period (in dollars)	$21,721	'	$21,721	'
Aggregate Intrinsic Value Exercisable at the end of the period (in dollars)	10,796	'	10,796	'
Grant-Date Fair value	'	'	'	'
Number of options exercised (in shares)	'	'	201,295	505,057
Cash received from option exercises	'	'	10,168	10,410
Intrinsic value of stock options exercised	'	'	6,811	20,232
Grant date fair value of options vested	'	'	$2,521	$2,466
Granted (in dollars per share)	$21.64	$20.55	$21.64	$20.55
Non-vested Stock Options	'	'	'	'
Non-vested at the beginning of the period (in shares)	'	'	317,062	'
Granted (in shares)	144,400	152,800	144,400	152,800
Vested (in shares)	'	'	-96,337	'
Forfeited (in shares)	'	'	-15,443	'
Non-vested at the end of the period (in shares)	349,682	'	349,682	'
Weighted Average Grant Date Fair Value - Non-Vested Stock Options	'	'	'	'
Non-vested at the beginning of the period (in dollars per share)	'	'	$23.22	'
Granted (in dollars per share)	$21.64	$20.55	$21.64	$20.55
Vested (in dollars per share)	'	'	$26.17	'
Forfeited (in dollars per share)	'	'	$25.96	'
Non-vested at the end of the period (in dollars per share)	$21.63	'	$21.63	'
Weighted Average Exercise Price - Non-Vested Stock Options	'	'	'	'
Non-vested at the beginning of the period (in dollars per share)	'	'	$60.58	'
Granted (in dollars per share)	'	'	$72.25	'
Vested (in dollars per share)	'	'	$65.54	'
Forfeited (in dollars per share)	'	'	$65.51	'
Non-vested at the end of the period (in dollars per share)	$63.82	'	$63.82	'
Maximum	'	'	'	'
Grant-Date Fair value	'	'	'	'
Vesting period	'	'	'5 years	'
Term of options from grant to expiration	'	'	'10 years	'
Minimum	'	'	'	'
Grant-Date Fair value	'	'	'	'
Vesting period	'	'	'3 years	'
Term of options from grant to expiration	'	'	'7 years	'

Asset_Retirement_Obligations_D

Asset Retirement Obligations (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Asset Retirement Obligations	'
Balance at beginning of year	$185,138
Liabilities incurred	4,272
Liability settlements and disposals	-41,540
Accretion expense	5,987
Revisions of estimated liabilities	2,502
Balance at end of year	156,359
Less current obligation	-49,435
Long-term asset retirement obligation	$106,924

LongTerm_Debt_Details

Long-Term Debt (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Apr. 30, 2012
In Thousands, unless otherwise specified
Debt Instrument	'	'	'
Long-term debt	$900,000	$750,000	'
Bank debt	'	'	'
Debt Instrument	'	'	'
Long-term debt	150,000	'	'
5.875% Notes due 2022	'	'	'
Debt Instrument	'	'	'
Long-term debt	$750,000	$750,000	$750,000
Interest rate (as a percent)	5.88%	5.88%	5.88%

LongTerm_Debt_Details_2

Long-Term Debt (Details 2) (USD $)

9 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

31-May-07

Jun. 30, 2012

Mar. 22, 2012

Sep. 30, 2013

Dec. 31, 2012

Apr. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Bank debt

Bank debt

7.125% Notes due 2017

7.125% Notes due 2017

7.125% Notes due 2017

5.875% Notes due 2022

5.875% Notes due 2022

5.875% Notes due 2022

LIBOR

LIBOR

Federal funds rate

One-month adjusted LIBOR rate

Minimum

Bank debt

Bank debt

Bank debt

Bank debt

Minimum

Maximum

Debt Instrument

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit facility term

'

'

'

'5 years

'

'

'

'

'

'

'

'

'

'

'

Borrowing base of credit facility

'

'

'

$2,250,000,000

'

'

'

'

'

'

'

'

'

'

'

Bank commitments of credit facility

'

'

'

1,000,000,000

'

'

'

'

'

'

'

'

'

'

'

Long-term debt

'

900,000,000

750,000,000

150,000,000

'

'

'

'

750,000,000

750,000,000

750,000,000

'

'

'

'

Weighted average interest rate (as a percent)

'

'

'

2.28%

'

'

'

'

'

'

'

'

'

'

'

Letters of credit outstanding under the credit facility

'

'

'

2,500,000

'

'

'

'

'

'

'

'

'

'

'

Unused borrowing availability

'

'

'

847,500,000

'

'

'

'

'

'

'

'

'

'

'

Interest rate margin (as a percent)

'

'

'

'

'

'

'

'

'

'

'

1.75%

2.50%

0.50%

1.00%

Additional interest rate margin, low end of range (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.75%

Additional interest rate margin, high end of range (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.50%

Current ratio to be maintained under credit facility

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

Maximum leverage ratio

'

'

'

3.5

'

'

'

'

'

'

'

'

'

'

'

Interest rate (as a percent)

'

'

'

'

'

7.13%

'

7.13%

5.88%

5.88%

5.88%

'

'

'

'

Redemption price of fifth year (as a percent)

'

'

'

'

'

'

'

'

'

'

102.94%

'

'

'

'

Redemption price of eighth year and thereafter (as a percent)

'

'

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

Issuance of senior unsecured notes

'

'

'

'

'

350,000,000

'

'

'

'

'

'

'

'

'

Loss on early extinguishment of debt

$16,214,000

'

'

'

'

'

($16,200,000)

'

'

'

'

'

'

'

'

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Components of provision for income taxes (in thousands):	'	'	'	'	'
Current benefit	'	($1,629,000)	'	($1,629,000)	'
Deferred taxes	81,823,000	49,568,000	211,615,000	150,648,000	'
Total income tax expense (benefits)	81,823,000	47,939,000	211,615,000	149,019,000	'
U.S. net tax operating loss carryforward	'	'	'	'	480,700,000
Alternative minimum tax credit carryforward	'	'	'	'	4,400,000
Unrecognized tax benefits that would impact the entity's effective rate	0	'	0	'	'
Provisions for interest or penalties related to uncertain tax positions	$0	'	$0	'	'
U.S. statutory rate (as a percent)	'	'	35.00%	'	'
Effective income tax rates (as a percent)	'	'	37.20%	36.90%	'

Supplemental_Disclosure_of_Cas2

Supplemental Disclosure of Cash Flow Information: (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Cash paid during the period for:	'	'	'	'
Interest expense (including capitalized amounts)	$1,932	$1,017	$27,158	$15,374
Interest capitalized	394	432	15,706	11,304
Income taxes	'	'	205	375
Cash received for income taxes	$213	$57	$450	$49,293

Earnings_per_Share_Details

Earnings per Share (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic:	'	'	'	'
Net income	$138,370	$84,262	$357,862	$254,671
Participating securities' share in earnings (in dollars)	-2,375	-1,628	-6,049	-4,929
Net income applicable to common shareholders	135,995	82,634	351,813	249,742
Diluted:	'	'	'	'
Net income	138,370	84,262	357,862	254,671
Participating securities' share in earnings (in dollars)	-2,371	-1,622	-6,041	-4,910
Net income applicable to common shareholders	$135,999	$82,640	$351,821	$249,761
Shares:	'	'	'	'
Basic shares outstanding	85,213	84,681	85,213	84,681
Incremental shares from assumed exercise of stock options	134	316	117	340
Fully diluted common stock (in shares)	85,347	84,997	85,330	85,021
Excluded antidilutive securities (in shares)	232	400	254	408
Earnings per share to common shareholders	'	'	'	'
Basic (in dollars per share)	$1.59	$0.97	$4.12	$2.94
Diluted (in dollars per share)	$1.59	$0.97	$4.12	$2.93

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Drilling Commitments	'
Construction, Drilling and Purchase Commitments	'
Commitments for purchases and other expenditures	$176.90
Construction of gathering facilities and pipelines	'
Construction, Drilling and Purchase Commitments	'
Commitments for purchases and other expenditures	$4.10

Commitments_and_Contingencies_2

Commitments and Contingencies (Details 2) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Non-cancelable operating leases	'
Future minimum operating lease arrangements	$130.70
Natural Gas Sales Contracts	'
Delivery Commitments	'
Volume of gas deliverable (in Bcf)	25,000
Delivery term	'11 months
Financial commitment upon nondelivery	82.8
Other transportation and delivery commitments	'
Delivery Commitments	'
Delivery term	'4 years
Financial commitment upon nondelivery	$3.50

Commitments_and_Contingencies_3

Commitments and Contingencies (Details 3) (USD $)	9 Months Ended	0 Months Ended	3 Months Ended	1 Months Ended		12 Months Ended
	Sep. 30, 2013	Dec. 11, 2012	Dec. 31, 2012	Aug. 31, 2011	Jan. 31, 2009	Dec. 31, 2008
		Hitch Enterprises, Inc., et al. v. Cimarex Energy Co., et al.	Hitch Enterprises, Inc., et al. v. Cimarex Energy Co., et al.	H.B. Krug, et al versus H&P	H.B. Krug, et al versus H&P	H.B. Krug, et al versus H&P
Loss Contingencies	'	'	'	'	'	'
Preliminary resolution amount	'	$16,400,000	'	'	'	'
Accrued litigation expense	'	'	16,400,000	'	'	119,600,000
Award to plaintiff, damages and disgorgement	'	'	'	'	119,600,000	'
Initial award to plaintiff, disgorgement	'	'	'	112,700,000	'	'
Award to plaintiff, damages	'	'	'	6,845,000	'	'
Changes in accrued liabilities	'	'	'	'	'	'
Accrued liabilities related to lawsuit at beginning of period	155,374,000	'	'	'	'	'
Accrued post-judgment interest and costs	7,070,000	'	'	'	'	'
Accrued liabilities related to lawsuit at ending of period	$162,444,000	'	'	'	'	'

Property_Sales_and_Acquisition1

Property Sales and Acquisitions (Details) (USD $)	9 Months Ended		3 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013
			Triple Crown gas gathering and processing system
Property Sales	'	'	'
Sale of interests in oil and gas properties	$37,700,000	$12,200,000	'
Sales of other assets	31,252,000	550,000	31,000,000
Interest sold in property (as a percent)	'	'	50.00%
Acquisition of interest in oil and gas properties	$6,200,000	$11,300,000	'