Athlon Energy (ATHL) Inactive 10-K7 Mar 142013 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
Document and Entity Information (USD $)	Dec. 31, 2013	Mar. 07, 2014	Aug. 02, 2013
Document and Entity Information	'	'	'
Entity Registrant Name	'Athlon Energy Inc.	'	'
Entity Central Index Key	'0001574648	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Amendment Flag	'false	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'No	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Filer Category	'Non-accelerated Filer	'	'
Entity Public Float	'	'	$410,526,324
Entity Common Stock, Shares Outstanding	'	82,129,089	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current assets:	'	'
Cash and cash equivalents	$113,025	$8,871
Accounts receivable	48,238	24,501
Derivatives, at fair value	'	2,246
Inventory	928	1,022
Deferred taxes	380	'
Other	1,166	2,486
Total current assets	163,737	39,126
Oil and natural gas properties and equipment, at cost - full cost method:	'	'
Evaluated, including wells and related equipment	1,244,178	788,571
Unevaluated	89,859	89,860
Accumulated depletion, depreciation, and amortization	-160,779	-73,824
Oil and natural gas properties and equipment, net	1,173,258	804,607
Derivatives, at fair value	2,330	2,854
Debt issuance costs	14,679	4,418
Other	1,447	1,293
Total assets	1,355,451	852,298
Accounts payable:	'	'
Trade	459	3,170
Affiliate	'	935
Accrued liabilities:	'	'
Lease operating	6,563	3,858
Production, severance, and ad valorem taxes	2,550	1,307
Development capital	68,059	39,483
Interest	7,790	834
Derivatives, at fair value	8,354	592
Revenue payable	20,513	9,330
Deferred taxes	'	58
Other	4,035	1,808
Total current liabilities	118,323	61,375
Derivatives, at fair value	'	519
Asset retirement obligations, net of current portion	6,795	5,049
Long-term debt	500,000	362,000
Deferred taxes	92,397	2,340
Other	101	138
Total liabilities	717,616	431,421
Commitments and contingencies	'	'
Equity:	'	'
Partners' equity	'	420,877
Preferred stock, $.01 par value, at December 31, 2013, 50,000,000 shares authorized, none issued and outstanding	'	'
Common stock, $.01 par value, at December 31, 2013, 500,000,000 shares authorized, 82,129,089 issued and outstanding	821	'
Additional paid-in capital	593,943	'
Retained earnings	32,283	'
Total stockholders' equity	627,047	'
Noncontrolling interest	10,788	'
Total equity	637,835	420,877
Total liabilities and equity	$1,355,451	$852,298

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2013
CONSOLIDATED BALANCE SHEETS	'
Preferred stock, par value (in dollars per share)	$0.01
Preferred stock, shares authorized	50,000,000
Preferred stock, shares issued	0
Preferred stock, shares outstanding	0
Common stock, par value (in dollars per share)	$0.01
Common stock, shares authorized	500,000,000
Common stock, shares issued	82,129,089
Common stock, shares outstanding	82,129,089

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:	'	'	'
Oil	$252,606	$128,081	$51,193
Natural gas	16,620	8,415	3,521
Natural gas liquids	30,147	20,615	10,967
Total revenues	299,373	157,111	65,681
Production:	'	'	'
Lease operating	33,776	25,503	13,328
Production, severance, and ad valorem taxes	19,048	10,438	4,727
Processing, gathering, and overhead	222	84	60
Depletion, depreciation, and amortization	87,171	54,456	19,747
General and administrative	21,331	9,678	7,724
Contract termination fee	2,408	'	'
Acquisition costs	421	876	9,519
Derivative fair value loss (gain)	18,115	-9,293	7,959
Accretion of discount on asset retirement obligations	675	478	344
Total expenses	183,167	92,220	63,408
Operating income	116,206	64,891	2,273
Other income (expenses):	'	'	'
Interest	-36,669	-9,951	-2,945
Other	35	2	13
Total other expenses	-36,634	-9,949	-2,932
Income (loss) before income taxes	79,572	54,942	-659
Income tax provision	19,150	1,928	470
Consolidated net income (loss)	60,422	53,014	-1,129
Less: net income attributable to noncontrolling interest	1,359	'	'
Net income (loss) attributable to stockholders	$59,063	$53,014	($1,129)
Net income (loss) per common share:	'	'	'
Basic (in dollars per share)	$0.80	$0.80	($0.02)
Diluted (in dollars per share)	$0.80	$0.78	($0.02)
Weighted average common shares outstanding:	'	'	'
Basic (in shares)	72,915	66,340	66,340
Diluted (in shares)	74,771	68,196	66,340

CONSOLIDATED_STATEMENT_OF_CHAN

CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (USD $)	Total	Total Stockholders' Equity	Partners' Equity	Common Stock	Additional Paid-in Capital	Retained Earnings	Noncontrolling Interest
In Thousands, except Share data, unless otherwise specified	Total	Total Stockholders' Equity	Partners' Equity	Common Stock	Additional Paid-in Capital	Retained Earnings	Noncontrolling Interest
Balance at Dec. 31, 2010	'	'	$24,499	'	'	'	'
Balance at Dec. 31, 2010	24,499	'	'	'	'	'	'
Increase (Decrease) in Equity	'	'	'	'	'	'	'
Capital contributions	303,976	'	303,976	'	'	'	'
Equity-based compensation prior to corporate reorganization	106	'	106	'	'	'	'
Net income (loss) prior to corporate reorganization	-1,129	'	-1,129	'	'	'	'
Balance at Dec. 31, 2011	'	'	327,452	'	'	'	'
Balance at Dec. 31, 2011	327,452	'	'	'	'	'	'
Increase (Decrease) in Equity	'	'	'	'	'	'	'
Capital contributions	40,166	'	40,166	'	'	'	'
Equity-based compensation prior to corporate reorganization	245	'	245	'	'	'	'
Net income (loss) prior to corporate reorganization	53,014	'	53,014	'	'	'	'
Balance at Dec. 31, 2012	420,877	'	420,877	'	'	'	'
Balance at Dec. 31, 2012	420,877	'	'	'	'	'	'
Increase (Decrease) in Equity	'	'	'	'	'	'	'
Capital contributions	1,500	'	1,500	'	'	'	'
Equity-based compensation prior to corporate reorganization	89	'	89	'	'	'	'
Net income (loss) prior to corporate reorganization	26,780	'	26,780	'	'	'	'
Distributions to Athlon Holdings LP's Class A limited partners	-75,000	'	-75,000	'	'	'	'
Common stock issued in corporate reorganization	'	364,817	-374,246	663	364,154	'	9,429
Common stock issued in corporate reorganization (in shares)	'	'	'	66,340,000	'	'	'
Tax impact of corporate reorganization	-71,605	-71,605	'	'	-71,605	'	'
Shares of common stock sold in initial public offering, net of offering costs	295,656	295,656	'	158	295,498	'	'
Shares of common stock sold in initial public offering, net of offering costs (in shares)	'	'	'	15,789,000	'	'	'
Equity-based compensation subsequent to corporate reorganization	5,896	5,896	'	'	5,896	'	'
Consolidated net income subsequent to corporate reorganization	33,642	32,283	'	'	'	32,283	1,359
Balance at Dec. 31, 2013	$637,835	$627,047	'	$821	$593,943	$32,283	$10,788
Balance (in shares) at Dec. 31, 2013	82,129,089	'	'	82,129,000	'	'	'

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:	'	'	'
Consolidated net income (loss)	$60,422	$53,014	($1,129)
Adjustments to reconcile consolidated net income (loss) to net cash provided by operating activities:	'	'	'
Depletion, depreciation, and amortization	87,171	54,456	19,747
Deferred taxes	18,015	1,928	470
Non-cash derivative loss (gain)	10,013	-9,947	7,509
Equity-based compensation	5,307	152	106
Other	5,575	1,758	963
Changes in operating assets and liabilities, net of effects from acquisitions:	'	'	'
Accounts receivable	-24,534	-7,320	-16,963
Other current assets	-71	-337	-1,691
Other assets	'	'	-16
Accounts payable	-2,583	-2,140	537
Accrued interest	6,956	578	256
Revenue payable	10,681	3,620	5,710
Derivatives	'	'	-1,950
Other current liabilities	6,685	-460	5,323
Net cash provided by operating activities	183,637	95,302	18,872
Cash flows from investing activities:	'	'	'
Acquisitions of oil and natural gas properties	-54,136	-80,602	-414,759
Development of oil and natural gas properties	-369,946	-266,235	-57,457
Monetization of put options	'	'	7,625
Other	-664	-422	-884
Net cash used in investing activities	-424,746	-347,259	-465,475
Cash flows from financing activities:	'	'	'
Proceeds from long-term debt, net of issuance costs	628,992	519,672	198,651
Payments on long-term debt	-505,926	-331,000	-31,000
Distributions to Athlon Holdings LP's Class A limited partners	-75,000	'	'
Shares of common stock sold in initial public offering, net of offering costs	295,697	'	'
Capital contributions	1,500	40,166	303,976
Other	'	-40	'
Net cash provided by financing activities	345,263	228,798	471,627
Increase (decrease) in cash and cash equivalents	104,154	-23,159	25,024
Cash and cash equivalents, beginning of period	8,871	32,030	7,006
Cash and cash equivalents, end of period	$113,025	$8,871	$32,030

Formation_of_the_Company_and_D

Formation of the Company and Description of Business	12 Months Ended
Formation of the Company and Description of Business	Dec. 31, 2013
Formation of the Company and Description of Business	'
Formation of the Company and Description of Business	'

	Note 1. Formation of the Company and Description of Business

	Athlon Energy Inc. (together with its subsidiaries, "Athlon"), a Delaware corporation, was formed on April 1, 2013 and is an independent exploration and production company focused on the acquisition, development, and exploitation of unconventional oil and liquids-rich natural gas reserves in the Permian Basin.

	On April 26, 2013, Athlon Holdings LP (together with its subsidiaries, "Holdings"), a Delaware limited partnership, underwent a corporate reorganization and as a result, Holdings became a majority-owned subsidiary of Athlon. Holdings is considered Athlon's accounting predecessor. Athlon operates and controls all of the business and affairs of Holdings and consolidates its financial results. Holdings is not subject to federal income taxes. On the date of the corporate reorganization, a corresponding "first day" net deferred tax liability of approximately $71.6 million was recorded for differences between the tax and book basis of Athlon's assets and liabilities. The offset of the deferred tax liability was recorded to additional paid-in capital.

	Prior to the corporate reorganization, Holdings was a party to a limited partnership agreement with its management group and Apollo Athlon Holdings, L.P. ("Apollo"), which is an affiliate of Apollo Global Management, LLC. Prior to the corporate reorganization, Apollo Investment Fund VII, L.P. and its parallel funds (the "Apollo Funds") and Holdings' management team and certain employees owned all of the Class A limited partner interests in Holdings and Holdings' management team and certain employees owned all of the Class B limited partner interests in Holdings.

	In the corporate reorganization, the Apollo Funds entered into a number of distribution and contribution transactions pursuant to which the Apollo Funds exchanged their Class A limited partner interests in Holdings for common stock of Athlon. The remaining holders of Class A limited partner interests in Holdings did not exchange their interests in the reorganization transactions. In addition, the holders of the Class B limited partner interests in Holdings exchanged their interests for common stock of Athlon subject to the same conditions and vesting terms.

	Initial Public Offering

	On August 7, 2013, Athlon completed its initial public offering ("IPO") of 15,789,474 shares of its common stock at $20.00 per share and received net proceeds of approximately $295.7 million, after deducting underwriting discounts and commissions and offering expenses. Upon closing of the IPO, the limited partnership agreement of Holdings was amended and restated to, among other things, modify Holdings' capital structure by replacing its different classes of interests with a single new class of units, the "New Holdings Units". Holdings' management team and certain employees that held Class A limited partner interests now own 1,855,563 New Holdings Units and entered into an exchange agreement under which (subject to the terms of the exchange agreement) they have the right to exchange their New Holdings Units for shares of common stock of Athlon on a one-for-one basis, subject to customary conversion rate adjustments for stock splits, stock dividends, and reclassifications. All other New Holdings Units are held by Athlon. Athlon used the net proceeds from the IPO (i) to reduce outstanding borrowings under its credit agreement, (ii) to provide additional liquidity for use in its drilling program, and (iii) for general corporate purposes.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Summary of Significant Accounting Policies	'

	Note 2. Summary of Significant Accounting Policies

	Principles of Consolidation

	Athlon's consolidated financial statements include the accounts of its wholly owned and majority-owned subsidiaries. All material intercompany balances and transactions have been eliminated in consolidation.

	Use of Estimates

	Preparing financial statements in conformity with accounting principles generally accepted in the United States requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses, and the disclosure of contingent assets and liabilities in the consolidated financial statements. Although management believes these estimates are reasonable, actual results could differ materially from those estimates.

	Estimates made in preparing these consolidated financial statements include, among other things, estimates of the proved oil and natural gas reserve volumes used in calculating depletion, depreciation, and amortization ("DD&A") expense; operating costs accrued; volumes and prices for revenues accrued; valuation of derivative instruments; and the timing and amount of future abandonment costs used in calculating asset retirement obligations. Changes in the assumptions used could have a significant impact on results in future periods.

	Cash and Cash Equivalents

	Cash and cash equivalents include demand deposits and funds invested in highly liquid instruments with original maturities of three months or less and typically exceed federally insured limits.

	The following table sets forth supplemental disclosures of cash flow information for the periods indicated:


			Year ended December 31,
			2013			2012			2011
			(in thousands)
	Cash paid during the period for:
	Interest		$	25,220		$	8,326		$	2,395
	Income taxes			—			—			—

	Accounts Receivable

	Accounts receivable, which are primarily from the sale of oil, natural gas, and natural gas liquids ("NGLs"), is accrued based on estimates of the sales and prices Athlon believes it will receive. Athlon routinely reviews outstanding balances, assesses the financial strength of its customers, and records a reserve for amounts not expected to be fully recovered. Actual balances are not applied against the reserve until substantially all collection efforts have been exhausted. At December 31, 2013 and 2012, Athlon did not have an allowance for doubtful accounts.

	Inventory

	Inventory includes materials and supplies that Athlon intends to deploy to various development activities and oil in tanks at the lease, both of which are stated at the lower of cost (determined on an average basis) or market. Oil in tanks at the lease is carried at an amount equal to its costs to produce. Inventory consisted of the following as of the dates indicated:


			December 31,
			2013			2012
			(in thousands)
	Materials and supplies		$	429		$	670
	Oil inventory			499			352


	Total inventory		$	928		$	1,022





	Oil and Natural Gas Properties

	Athlon applies the provisions of the "Extractive Activities—Oil and Gas" topic of the Financial Accounting Standards Board's (the "FASB") Accounting Standards Codification (the "ASC"). Athlon uses the full cost method of accounting for its oil and natural gas properties. Under this method, costs directly associated with the acquisition, exploration, and development of reserves are capitalized into a full cost pool. Capitalized costs are amortized using a unit-of-production method. Under this method, the provision for DD&A is computed at the end of each period by multiplying total production for the period by a depletion rate. The depletion rate is determined by dividing the total unamortized cost base plus future development costs by net equivalent proved reserves at the beginning of the period.

	Costs associated with unevaluated properties are excluded from the amortizable cost base until a determination has been made as to the existence of proved reserves. Unevaluated properties are reviewed at the end of each quarter to determine whether the costs incurred should be reclassified to the full cost pool and, thereby, subjected to amortization. The costs associated with unevaluated properties primarily consist of acquisition and leasehold costs as well as development costs for wells in progress for which a determination of the existence of proved reserves has not been made. These costs are transferred to the amortization base once a determination is made whether or not proved reserves can be assigned to the property, upon impairment of a lease, or immediately upon determination that the well is unsuccessful. Costs of seismic data that cannot be directly associated to specific properties are included in the full cost pool as incurred; otherwise, they are allocated to various unevaluated leaseholds and transferred to the amortization base with the associated leasehold costs on a specific project basis.

	Independent petroleum engineers estimate Athlon's proved reserves annually as of December 31. This results in a new DD&A rate which Athlon uses for the preceding fourth quarter after adjusting for fourth quarter production. Athlon internally estimates reserve additions and reclassifications of reserves from unproved to proved at the end of the first, second, and third quarters for use in determining a DD&A rate for the respective quarter.

	Sales and abandonments of oil and natural gas properties being amortized are accounted for as adjustments to the full cost pool, with no gain or loss recognized, unless the adjustments would significantly alter the relationship between capitalized costs and proved reserves. A significant alteration would not ordinarily be expected to occur upon the sale of reserves involving less than 25% of the reserve quantities of a cost center.

	Natural gas volumes are converted to barrels of oil equivalent ("BOE") at the rate of six thousand cubic feet ("Mcf") of natural gas to one barrel ("Bbl") of oil. This convention is not an equivalent price basis and there may be a large difference in value between an equivalent volume of oil versus an equivalent volume of natural gas.

	Athlon capitalizes interest on expenditures made in connection with exploratory projects that are not subject to current amortization. Interest is capitalized only for the period that activities are in progress to bring these projects to their intended use. Capitalized interest cannot exceed gross interest expense. During 2013 and 2012, Athlon capitalized approximately $0.3 million and $0.2 million, respectively, of interest expense. During 2011, Athlon did not capitalize any interest expense.

Unevaluated properties are assessed periodically, at least annually, for possible impairment. Properties are assessed on an individual basis or as a group if properties are individually insignificant. The assessment includes consideration of various factors, including, but not limited to: intent to drill, remaining lease term, geological and geophysical evaluations, drilling results, and economic viability of development if proved reserves are assigned. During any period in which these factors indicate impairment, the cumulative drilling costs incurred to date for such property and all or a portion of the associated leasehold costs are transferred to the full cost pool and become subject to amortization.

Under the full cost method of accounting, total capitalized costs of oil and natural gas properties, net of accumulated DD&A, less related deferred income taxes may not exceed an amount equal to the present value of future net revenues from proved reserves, discounted at 10% per annum, plus the lower of cost or fair value of unevaluated properties, plus estimated salvage value, less the related tax effects (the "ceiling limitation"). A ceiling limitation is calculated at the end of each quarter. If total capitalized costs, net of accumulated DD&A, less related deferred income taxes are greater than the ceiling limitation, a write-down or impairment of the full cost pool is required. A write-down of the carrying value of the full cost pool is a non-cash charge that reduces earnings and impacts equity in the period of occurrence and typically results in lower DD&A expense in future periods. Once incurred, a write-down cannot be reversed at a later date.

The ceiling limitation calculation is prepared using the 12-month first-day-of-the-month oil and natural gas average prices, as adjusted for basis or location differentials, held constant over the life of the reserves ("net wellhead prices"). If applicable, these net wellhead prices would be further adjusted to include the effects of any fixed price arrangements for the sale of oil and natural gas. Athlon uses commodity derivative contracts to mitigate the risk against the volatility of oil and natural gas prices. Commodity derivative contracts that qualify and are designated as cash flow hedges are included in estimated future cash flows. Athlon has not designated any of its commodity derivative contracts as cash flow hedges and therefore has excluded commodity derivative contracts in estimating future cash flows. The future cash outflows associated with future development or abandonment of wells are included in the computation of the discounted present value of future net revenues for purposes of the ceiling limitation calculation.

Amounts shown in the accompanying Consolidated Balance Sheets as "Evaluated, including wells and related equipment" consisted of the following as of the dates indicated:


		December 31,
		2013			2012
		(in thousands)
Evalauted leasehold costs		$	448,689		$	376,271
Wells and related equipment—completed			748,900			379,036
Wells and related equipment—in process			46,589			33,264


Total evaluated		$	1,244,178		$	788,571





Asset Retirement Obligations

Athlon applies the provisions of the "Asset Retirement and Environmental Obligations" topic of the ASC. Athlon has obligations as a result of lease agreements and enacted laws to remove its equipment and restore land at the end of production operations. These asset retirement obligations are primarily associated with plugging and abandoning wells and land remediation. At the time a drilled well is completing or a well is acquired, Athlon records a separate liability for the estimated fair value of its asset retirement obligations, with an offsetting increase to the related oil and natural gas asset representing asset retirement costs in the accompanying Consolidated Balance Sheets. The cost of the related oil and natural gas asset, including the asset retirement cost, is included in Athlon's full cost pool. The estimated fair value of an asset retirement obligation is the present value of the expected future cash outflows required to satisfy the asset retirement obligations discounted at Athlon's credit-adjusted, risk-free interest rate at the time the liability is incurred. Accretion expense is recognized over time as the discounted liability is accreted to its expected settlement value.

Inherent to the present-value calculation are numerous estimates, assumptions, and judgments, including, but not limited to: the ultimate settlement amounts, inflation factors, credit-adjusted risk-free rates, timing of settlement, and changes in the legal, regulatory, environmental, and political environments. To the extent future revisions to these assumptions affect the present value of the abandonment liability, Athlon makes corresponding adjustments to both the asset retirement obligation and the related oil and natural gas property asset balance. These revisions result in prospective changes to DD&A expense and accretion of the discounted abandonment liability. Please read "Note 5. Asset Retirement Obligations" for additional information.

Equity-Based Compensation

Athlon accounts for equity-based compensation according to the "Share-Based Payment" topic of the ASC, which requires the recognition of compensation expense for equity-based awards over the requisite service period in an amount equal to the grant date fair value of the awards. Please read "Note 9. Employee Benefit Plans" for additional discussion of Athlon's employee benefit plans.

The "Share-Based Payment" topic of the ASC also requires that the benefits associated with the tax deductions in excess of recognized compensation cost, if any, be reported as a financing cash flow. This requirement reduces net operating cash flows and increases net financing cash flows. Athlon recognizes compensation costs related to awards with graded vesting on a straight-line basis over the requisite service period for each separately vesting portion of the award as if the award was, in substance, multiple awards.

Segment Reporting

Athlon only operates in the oil and natural gas exploration and production industry in the United States. All revenues are derived from customers located in the United States.

Major Customers / Concentration of Credit Risk

The following purchasers accounted for 10% or greater of the sales of production for the periods indicated and the corresponding outstanding accounts receivable balance as of the dates indicated:


		Percentage of Total									Outstanding
		Revenues for									Accounts
		the Year Ended									Receivable Balance
		December 31,									as of December 31,
Purchaser		2013			2012			2011			2013			2012
											(in thousands)
Occidental Petroleum Corporation			27	%		29	%		58	%	$	11,673		$	4,456
DCP Midstream				(a)		12	%		13	%			(a)		2,604
High Sierra Crude Oil & Marketing, LLC(b)			46	%		43	%		13	%		18,951			9,348


(a)
Less than 10% for the period indicated.

(b)
Formerly Pecos Gathering & Marketing.

Income Taxes

Athlon accounts for income taxes using the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax laws and rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.

Athlon periodically assesses whether it is more likely than not that it will generate sufficient taxable income to realize its deferred income tax assets, including net operating losses. In making this determination, Athlon considers all available positive and negative evidence and makes certain assumptions. Athlon considers, among other things, its deferred tax liabilities, the overall business environment, its historical earnings and losses, current industry trends, and its outlook for future years. Athlon believes it is more likely than not that certain net operating losses can be carried forward and utilized.

In April 2013, Athlon effected a corporate reorganization. Holdings, Athlon's accounting predecessor, is a partnership not subject to federal income tax. Pursuant to the corporate reorganization, certain Class A limited partners and the Class B limited partners of Holdings exchanged their interests for shares of Athlon's common stock. Athlon's operations are now subject to federal income tax. The tax implications of the corporate reorganization and the tax impact of the conversion to operating as a taxable entity have been reflected in the accompanying consolidated financial statements.

Revenue Recognition

Revenues from the sale of oil, natural gas, and NGLs are recognized when they are realized or realizable and earned. Revenues are considered realized or realizable and earned when: (i) persuasive evidence of an arrangement exists; (ii) delivery has occurred or services have been rendered; (iii) the seller's price to the buyer is fixed or determinable; and (iv) collectability is reasonably assured. Because final settlement of our hydrocarbon sales can take up to two months, sales volumes and prices are estimated and accrued using information available at the time the revenue is recorded. If Athlon's overproduced imbalance position (i.e., Athlon has cumulatively been over-allocated production) is greater than its share of remaining reserves, a liability would be recorded for the excess at period-end prices unless a different price is specified in the contract, in which case that price is used. At December 31, 2013 and 2012, Athlon did not have any natural gas imbalances. Revenue is not recognized for oil production in tanks, but the production is recorded as a current asset based on the cost to produce and included in "Inventory" in the accompanying Consolidated Balance Sheets. Transportation expenses are included in operating expenses and are insignificant.

Derivatives

Athlon uses various financial instruments for non-trading purposes to manage and reduce price volatility and other market risks associated with its oil production. These arrangements are structured to reduce Athlon's exposure to commodity price decreases, but they can also limit the benefit Athlon might otherwise receive from commodity price increases. Athlon's risk management activity is generally accomplished through over-the-counter commodity derivative contracts with large financial institutions, most of which are lenders under Athlon's credit agreement.

Athlon applies the provisions of the "Derivatives and Hedging" topic of the ASC, which requires each derivative instrument to be recorded in the accompanying Consolidated Balance Sheets at fair value. If a derivative has not been designated as a hedge or does not otherwise qualify for hedge accounting, it must be adjusted to fair value through earnings. Athlon elected not to designate its current portfolio of commodity derivative contracts as hedges for accounting purposes. Therefore, changes in fair value of these derivative instruments are recognized in earnings and included in "Derivative fair value loss (gain)" in the accompanying Consolidated Statements of Operations.

Athlon enters into commodity derivative contracts for the purpose of economically fixing the price of its anticipated oil production even though Athlon does not designate the derivatives as hedges for accounting purposes. Athlon classifies cash flows related to derivative contracts based on the nature and purpose of the derivative. As the derivative cash flows are considered an integral part of Athlon's oil and natural gas operations, they are classified as cash flows from operating activities in the accompanying Consolidated Statements of Cash Flows.

Noncontrolling Interest

As of December 31, 2013, management and certain employees owned approximately 2.2% of Holdings. Athlon owns 100% of Athlon Holdings GP LLC, which is Holdings' general partner. Considering the presumption of control, Athlon has fully consolidated the financial position, results of operations, and cash flows of Holdings.

As presented in the accompanying Consolidated Balance Sheets, "Noncontrolling interest" as of December 31, 2013 of approximately $10.8 million represents management and certain employees' 1,855,563 New Holdings Units that are exchangeable for shares of Athlon's common stock on a one-for-one basis. As presented in the accompanying Consolidated Statements of Operations, "Net income attributable to noncontrolling interest" for 2013 of approximately $1.4 million represents the net income of Holdings attributable to management and certain employees since April 26, 2013.

The following table summarizes the effects of changes in Athlon's partnership interest in Holdings on Athlon's equity for 2013 (in thousands):


Net income attributable to stockholders		$	59,063


Transfer from noncontrolling interest:
Increase in Athlon's paid-in capital for corporate reorganization			292,549
Increase in Athlon's paid-in capital for issuance of 15,789,474 shares of common stock in initial public offering			295,498


Net transfer from noncontrolling interest			588,047


Change from net income attributable to stockholders and transfers from noncontrolling interest		$	647,110





Earnings Per Share

For purposes of calculating earnings per share ("EPS"), Athlon allocates net income (loss) to its shareholders and participating securities each quarter under the provisions of the "Earnings Per Share" topic of the ASC. Under the two-class method of calculating EPS, earnings are allocated to participating securities as if all the earnings for the period had been distributed. A participating security is any security that may participate in distributions with common shares. For purposes of calculating EPS, unvested restricted stock units are considered participating securities. Net income (loss) per common share is calculated by dividing the shareholders' interest in net income (loss), after deducting the interests of participating securities, by the weighted average common shares outstanding.

New Accounting Pronouncements

In December 2011, the FASB issued Accounting Standards Update ("ASU") 2011-11, "Disclosures about Offsetting Assets and Liabilities" and in January 2013 issued ASU 2013-01, "Clarifying the Scope of Disclosures About Offsetting Assets and Liabilities". These ASUs created new disclosure requirements regarding the nature of an entity's rights of offset and related arrangements associated with its derivative instruments, repurchase agreements, and securities lending transactions. Certain disclosures of the amounts of certain instruments subject to enforceable master netting arrangements are required, irrespective of whether the entity has elected to offset those instruments in the statement of financial position. These ASUs were effective retrospectively for annual reporting periods beginning on or after January 1, 2013. The adoption of these ASUs did not impact Athlon's financial position, results of operations, or liquidity.

No other new accounting pronouncements issued or effective from January 1, 2013 through the date of this Report, had or are expected to have a material impact on Athlon's consolidated financial statements.

Acquisitions

Acquisitions	12 Months Ended
Acquisitions	Dec. 31, 2013
Acquisitions	'
Acquisitions	'

	Note 3. Acquisitions

	Element

	On October 3, 2011, Athlon acquired certain oil and natural gas properties and related assets in the Permian Basin in West Texas from Element Petroleum, LP ("Element") for approximately $253.2 million in cash, which was financed through borrowings under Athlon's credit agreement and capital contributions from Holdings' partners. The operations of these properties have been included with those of Athlon from the date of acquisition. Athlon incurred approximately $6.4 million of transaction costs related to this acquisition, which are included in "Acquisition costs" in the accompanying Consolidated Statements of Operations. Of this amount, approximately $4.3 million was paid to Apollo. Please read "Note 12. Related Party Transactions" for additional discussion.

	The allocation of the purchase price to the fair value of the assets acquired and liabilities assumed from Element was as follows (in thousands):


	Proved properties, including wells and related equipment		$	130,527
	Unproved properties			123,107
	Other assets			806


	Total assets acquired			254,440


	Current liabilities			831
	Asset retirement obligations			393


	Total liabilities assumed			1,224


	Fair value of net assets acquired		$	253,216





	The following unaudited pro forma condensed financial data was derived from the historical financial statements of Athlon and from the accounting records of Element to give effect to the acquisition as if it had occurred on January 1, 2011. The unaudited pro forma condensed financial information has been included for comparative purposes only and is not necessarily indicative of the results that might have occurred had the Element acquisition taken place on January 1, 2011 and is not intended to be a projection of future results.


			Year ended
			December 31, 2011
			(in thousands, except
			per share amounts)
	Pro forma total revenues		$	89,618




	Pro forma net income attributable to stockholders		$	9,777




	Pro forma net income per common share:
	Basic		$	0.15
	Diluted		$	0.14

	SandRidge

	On January 6, 2011, Athlon acquired certain oil and natural gas properties and related assets in the Permian Basin in West Texas from SandRidge Exploration and Production, LLC ("SandRidge") for approximately $156.0 million in cash, which was financed through borrowings under Athlon's credit agreement and capital contributions from Holdings' partners. The operations of these properties have been included with those of Athlon from the date of acquisition. Athlon incurred $2.6 million of transaction costs related to this acquisition, which are included in "Acquisition costs" in the accompanying Consolidated Statements of Operations. Of this amount, approximately $2.3 million was paid to Apollo. Please read "Note 12. Related Party Transactions" for additional discussion.

	The allocation of the purchase price to the fair value of the assets acquired and liabilities assumed from SandRidge was as follows (in thousands):


	Proved properties, including wells and related equipment		$	158,157
	Oil inventory			637


Total assets acquired			158,794
Asset retirement obligations			2,778


Fair value of net assets acquired		$	156,016

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2013
Fair Value Measurements	'
Fair Value Measurements	'

	Note 4. Fair Value Measurements

	The book values of cash and cash equivalents, accounts receivable, and accounts payable approximate fair value due to the short-term nature of these instruments. Commodity derivative contracts are marked-to-market each quarter and are thus stated at fair value in the accompanying Consolidated Balance Sheets. As of December 31, 2013, the fair value of the senior notes was approximately $522.8 million using open market quotes ("Level 1" input).

	Commodity Derivative Contracts

	Commodity prices are often subject to significant volatility due to many factors that are beyond Athlon's control, including but not limited to: prevailing economic conditions, supply and demand of hydrocarbons in the marketplace, actions by speculators, and geopolitical events such as wars or natural disasters. Athlon manages oil price risk with swaps, which provide a fixed price for a notional amount of sales volumes. The following table summarizes Athlon's open commodity derivative contracts as of December 31, 2013:


	Period		Average			Weighted-			Asset
			Daily			Average			(Liability)
			Swap			Swap			Fair Market
			Volume			Price			Value
			(Bbl)			(per Bbl)			(in thousands)
	2014			7,950		$	92.67		$	(8,354	)
	2015			1,300			93.18			2,330


									$	(6,024	)





	In January 2011, Athlon terminated certain oil puts that were in place at December 31, 2010 and received net proceeds of approximately $7.6 million, which is reflected as "Monetization of put options" in the "Investing activities" section of the accompanying Consolidated Statements of Cash Flows. In the third quarter of 2011, Athlon entered into additional oil puts that included deferred premiums. These deferred premiums increased Athlon's interest expense by approximately $0.2 million during 2011. In October 2011, Athlon terminated the oil puts and entered into oil swaps that required the initial payment of premiums of approximately $2.0 million.

	Counterparty Risk. At December 31, 2013, Athlon had committed 10% or greater (in terms of fair market value) of its oil derivative contracts in asset positions from the following counterparties:


	Counterparty		Fair Market Value of
			Oil Derivative
			Contracts
			Committed
			(in thousands)
	BNP Paribas		$	1,082

	Athlon does not require collateral from its counterparties for entering into financial instruments, so in order to mitigate the credit risk associated with financial instruments, Athlon enters into master netting agreements with its counterparties. The master netting agreement is a standardized, bilateral contract between a given counterparty and Athlon. Instead of treating each financial transaction between the counterparty and Athlon separately, the master netting agreement enables the counterparty and Athlon to aggregate all financial trades and treat them as a single agreement. This arrangement is intended to benefit Athlon in two ways: (i) default by a counterparty under a single financial trade can trigger rights to terminate all financial trades with such counterparty; and (ii) netting of settlement amounts reduces Athlon's credit exposure to a given counterparty in the event of close-out. Athlon's accounting policy is to not offset fair value amounts between different counterparties for derivative instruments in the accompanying Consolidated Balance Sheets.

	Tabular Disclosures of Fair Value Measurements

	The following table summarizes the fair value of Athlon's derivative instruments not designated as hedging instruments as of the dates indicated:


	Balance Sheet Location		Oil			Commodity			Total
			Commodity			Derivatives			Commodity
			Derivatives			Netting(a)			Derivatives
			(in thousands)
	As of December 31, 2013
	Assets
	Derivatives—current		$	143		$	(143	)	$	—
	Derivatives—noncurrent			2,330			—			2,330


	Total assets			2,473			(143	)		2,330


	Liabilities
	Derivatives—current			(8,497	)		143			(8,354	)
	Derivatives—noncurrent			—			—			—


	Total liabilities			(8,497	)		143			(8,354	)


Net liabilities		$	(6,024	)	$	—		$	(6,024	)




As of December 31, 2012
Assets
Derivatives—current		$	3,386		$	(1,140	)	$	2,246
Derivatives—noncurrent			3,265			(411	)		2,854


Total assets			6,651			(1,551	)		5,100


Liabilities
Derivatives—current			(1,732	)		1,140			(592	)
Derivatives—noncurrent			(930	)		411			(519	)


Total liabilities			(2,662	)		1,551			(1,111	)


Net assets		$	3,989		$	—		$	3,989






(a)
Represents counterparty netting under master netting agreements, which allow for netting of commodity derivative contracts. These derivative instruments are reflected net on the accompanying Consolidated Balance Sheets.

The following table summarizes the effect of derivative instruments not designated as hedges on the accompanying Consolidated Statements of Operations for the periods indicated:


				Amount of Loss (Gain)
				Recognized in
				Income
				Year ended December 31,
		Location of Loss (Gain)		Year ended December 31,
Derivatives Not Designated as Hedges		Recognized in Income		2013			2012			2011
				(in thousands)
Commodity derivative contracts		Derivative fair value loss (gain)		$	18,115		$	(9,293	)	$	7,959

Fair Value Hierarchy

Fair value is defined as 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. Accounting principles generally accepted in the United States ("GAAP") establishes a three-tier fair value hierarchy, which prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are defined as follows:



•
Level 1—Inputs such as unadjusted, quoted prices that are available in active markets for identical assets or liabilities.

•
Level 2—Inputs, other than quoted prices within Level 1, that are either directly or indirectly observable, such as quoted prices for similar assets and liabilities or quoted prices in inactive markets.

•
Level 3—Inputs that are unobservable for use when little or no market data exists requiring the use of valuation methodologies that result in management's best estimate of fair value.

As required by GAAP, Athlon utilizes the most observable inputs available for the valuation technique used. The financial assets and liabilities are classified in their entirety based on the lowest level of input that is of significance to the fair value measurement. Athlon's assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of the financial assets and liabilities and their placement within the fair value hierarchy levels. The following methods and assumptions were used to estimate the fair values of Athlon's assets and liabilities that are accounted for at fair value on a recurring basis:



•
Level 2—Fair values of swaps are estimated using a combined income-based and market-based valuation methodology based upon forward commodity price curves obtained from independent pricing services. Settlement is determined by the average underlying price over a predetermined period of time. Athlon uses observable inputs in an option pricing valuation model to determine fair value such as: (i) current market and contractual prices for the underlying instruments; (ii) quoted forward prices for oil; (iii) interest rates, such as a LIBOR curve for a term similar to the commodity derivative contract; and (iv) appropriate volatilities.

Athlon adjusts the valuations from the valuation model for nonperformance risk. For commodity derivative contracts which are in an asset position, Athlon adds the counterparty's credit default swap spread to the risk-free rate. If a counterparty does not have a credit default swap spread, Athlon uses other companies with similar credit ratings to determine the applicable spread. For commodity derivative contracts which are in a liability position, Athlon uses the yield on its senior notes less the risk-free rate. All fair values have been adjusted for nonperformance risk resulting in a decrease in the net commodity derivative liability of approximately $39,000 as of December 31, 2013 and an increase in the net commodity derivative asset of approximately $125,000 as of December 31, 2012.

The following table sets forth Athlon's assets and liabilities that were accounted for at fair value on a recurring basis as of the dates indicated:


					Fair Value Measurements at Reporting Date Using
Description		Net Asset (Liability)			Quoted Prices in			Significant Other			Significant
					Active Markets for			Observable Inputs			Unobservable Inputs
					Identical Assets			(Level 2)			(Level 3)
					(Level 1)
		(in thousands)
As of December 31, 2013
Oil derivative contracts—swaps		$	(6,024	)	$	—		$	(6,024	)	$	—
As of December 31, 2012
Oil derivative contracts—swaps		$	4,069		$	—		$	4,069		$	—
Oil derivative contracts—collars			(80	)		—			(80	)		—


Total		$	3,989		$	—		$	3,989		$	—

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
Asset Retirement Obligations	Dec. 31, 2013
Asset Retirement Obligations	'
Asset Retirement Obligations	'

	Note 5. Asset Retirement Obligations

	Asset retirement obligations relate to future plugging and abandonment expenses on oil and natural gas properties and related facilities disposal. The following table summarizes the changes in Athlon's asset retirement obligations for the periods indicated:


		Year Ended
		December 31,
		2013			2012
		(in thousands)
	Balance at January 1	$	5,049		$	3,704
	Liabilities assumed in acquisitions		395			60
	Liabilities incurred from new wells		1,013			815
	Liabilities settled		(283	)		—
	Accretion of discount		675			478
	Revisions of previous estimates		6			(8	)


	Balance at December 31		6,855			5,049
	Less: current portion		60			—


	Asset retirement obligations—long-term	$	6,795		$	5,049

LongTerm_Debt

Long-Term Debt	12 Months Ended
Long-Term Debt	Dec. 31, 2013
Long-Term Debt.	'
Long-Term Debt	'

	Note 6. Long-Term Debt

	Senior Notes

	In April 2013, Athlon issued $500 million aggregate principal amount of 7³/8% senior notes due 2021 (the "Notes"). The net proceeds from the Notes were used to repay a portion of the outstanding borrowings under Athlon's credit agreement, to repay in full and terminate Athlon's former second lien term loan, to make a $75 million distribution to Holdings' Class A limited partners, and for general corporate purposes. On August 14, 2013, Holdings entered into a supplemental indenture pursuant to which Athlon became an unconditional guarantor of the Notes.

	The indenture governing the Notes contains covenants, including, among other things, covenants that restrict Athlon's ability to:



	•
	make distributions, investments, or other restricted payments if Athlon's fixed charge coverage ratio is less than 2.0 to 1.0;

	•
	incur additional indebtedness if Athlon's fixed charge coverage ratio would be less than 2.0 to 1.0; and

	•
	create liens, sell assets, consolidate or merge with any other person, or engage in transactions with affiliates.

	These covenants are subject to a number of important qualifications, limitations, and exceptions. In addition, the indenture contains other customary terms, including certain events of default upon the occurrence of which the senior notes may be declared immediately due and payable.

	Under the indenture, starting on April 15, 2016, Athlon will be able to redeem some or all of the Notes at a premium that will decrease over time, plus accrued and unpaid interest to the date of redemption. Prior to April 15, 2016, Athlon will be able, at its option, to redeem up to 35% of the aggregate principal amount of the Notes at a price of 107.375% of the principal thereof, plus accrued and unpaid interest to the date of redemption, with an amount equal to the net proceeds from certain equity offerings. In addition, at Athlon's option, prior to April 15, 2016, Athlon may redeem some or all of the Notes at a redemption price equal to 100% of the principal amount of the Notes, plus an "applicable premium", plus accrued and unpaid interest to the date of redemption. If a change of control occurs on or prior to July 15, 2014, Athlon may redeem all, but not less than all, of the notes at 110% of the principal amount thereof plus accrued and unpaid interest to, but not including, the redemption date. Certain asset dispositions will be triggering events that may require Athlon to repurchase all or any part of a noteholder's Notes at a purchase price in cash equal to 101% of the principal amount thereof, plus accrued and unpaid interest, if any, up to but excluding the date of repurchase. Interest on the Notes is payable in cash semi-annually in arrears, commencing on October 15, 2013, through maturity.

	As a result of the issuance of the Notes, Athlon's former second lien term loan was paid off and retired and the borrowing base of Athlon's credit agreement was reduced resulting in a write off of unamortized debt issuance costs of approximately $2.8 million, which is included in "Interest expense" in the accompanying Consolidated Statements of Operations and "Other" in the operating activities section of the accompanying Consolidated Statements of Cash Flows for 2013.

	Credit Agreement

	Athlon is a party to an amended and restated credit agreement dated March 19, 2013 (the "Credit Agreement"), which matures on March 19, 2018. The Credit Agreement provides for revolving credit loans to be made to Athlon from time to time and letters of credit to be issued from time to time for the account of Athlon or any of its restricted subsidiaries. The aggregate amount of the commitments of the lenders under the Credit Agreement is $1.0 billion. Availability under the Credit Agreement is subject to a borrowing base, which is redetermined semi-annually and upon requested special redeterminations.

	In conjunction with the offering of the Notes in April 2013 as discussed above, the borrowing base under the Credit Agreement was reduced to $267.5 million. In May 2013, Athlon amended the Credit Agreement to, among other things, increase the borrowing base to $320 million. In November 2013, Athlon amended the Credit Agreement to, among other things, increase the borrowing base to $525 million. As of December 31, 2013, the borrowing base was $525 million and there were no outstanding borrowings and no outstanding letters of credit under the Credit Agreement.

	Obligations under the Credit Agreement are secured by a first-priority security interest in substantially all of Athlon's proved reserves and in the equity interests of its operating subsidiaries. In addition, obligations under the Credit Agreement are guaranteed by Athlon's operating subsidiaries.

	Loans under the Credit Agreement are subject to varying rates of interest based on (i) outstanding borrowings in relation to the borrowing base and (ii) whether the loan is a Eurodollar loan or a base rate loan. Eurodollar loans under the Credit Agreement bear interest at the Eurodollar rate plus the applicable margin indicated in the following table, and base rate loans under the Credit Agreement bear interest at the base rate plus the applicable margin indicated in the following table. Athlon also incurs a quarterly commitment fee on the unused portion of the Credit Agreement indicated in the following table:


	Ratio of Outstanding Borrowings to Borrowing Base		Unused			Applicable			Applicable
			Commitment Fee			Margin for			Margin for Base
						Eurodollar Loans			Rate Loans
	Less than or equal to .30 to 1			0.375	%		1.5	%		0.5	%
	Greater than .30 to 1 but less than or equal to .60 to 1			0.375	%		1.75	%		0.75	%
	Greater than .60 to 1 but less than or equal to .80 to 1			0.5	%		2	%		1	%
	Greater than .80 to 1 but less than or equal to .90 to 1			0.5	%		2.25	%		1.25	%
	Greater than .90 to 1			0.5	%		2.5	%		1.5	%

	The "Eurodollar rate" for any interest period (either one, two, three, or nine months, as selected by Athlon) is the rate equal to the British Bankers Association London Interbank Offered Rate ("LIBOR") for deposits in dollars for a similar interest period. The "Base Rate" is calculated as the highest of: (i) the annual rate of interest announced by Bank of America, N.A. as its "prime rate"; (ii) the federal funds effective rate plus 0.5%; or (iii) except during a "LIBOR Unavailability Period", the Eurodollar rate (for dollar deposits for a one-month term) for such day plus 1.0%.

	Any outstanding letters of credit reduce the availability under the Credit Agreement. Borrowings under the Credit Agreement may be repaid from time to time without penalty.

	The Credit Agreement contains covenants including, among others, the following:



	•
	a prohibition against incurring debt, subject to permitted exceptions;

	•
	a restriction on creating liens on Athlon's assets and the assets of its operating subsidiaries, subject to permitted exceptions;

	•
	restrictions on merging and selling assets outside the ordinary course of business;



•
restrictions on use of proceeds, investments, transactions with affiliates, or change of principal business;

•
a requirement that Athlon maintain a ratio of consolidated total debt to EBITDAX (as defined in the Credit Agreement) of not more than 4.75 to 1.0 (which ratio changes to 4.5 to 1.0 beginning with the quarter ending June 30, 2014); and

•
a provision limiting commodity derivative contracts to a volume not exceeding 85% of projected production from proved reserves for a period not exceeding 66 months from the date the commodity derivative contract is entered into.

The Credit Agreement contains customary events of default, including Athlon's failure to comply with the financial ratios described above, which would permit the lenders to accelerate the debt if not cured within applicable grace periods. If an event of default occurs and is continuing, lenders with a majority of the aggregate commitments may require Bank of America, N.A. to declare all amounts outstanding under the Credit Agreement to be immediately due and payable.

Long-Term Debt Maturities

The following table shows Athlon's long-term debt maturities as of December 31, 2013:


		Payments Due by Period
		Total			2014			2015			2016		2017		2018		Thereafter
		(in thousands)
Credit Agreement		$	—		$	—		$	—		$	—	$	—	$	—	$	—
7³/8% Senior Notes			500,000			—			—			—		—		—		500,000


Total		$	500,000		$	—		$	—		$	—	$	—	$	—	$	500,000





During 2013, 2012, and 2011, the weighted-average interest rate for total indebtedness was 7.6%, 4.3%, and 3.8%, respectively.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2013
Stockholders' Equity	'
Stockholders' Equity	'

	Note 7. Stockholders' Equity

	In connection with Athlon's incorporation on April 1, 2013 under the laws of the State of Delaware, it issued 1,000 shares of its common stock to Athlon Holdings GP LLC for an aggregate purchase price of $10.00. These securities were offered and sold by Athlon in reliance upon the exemption from the registration requirements provided by Section 4(2) of the Securities Act of 1933. On April 26, 2013, in connection with the corporate reorganization, certain holders of limited partner interests in Holdings exchanged their Class A interests and Class B interests for an aggregate of 960,907 shares of Athlon's common stock. These securities were offered and sold by Athlon in reliance upon the exemption from the registration requirements provided by Section 4(2) of the Securities Act of 1933. In connection with the effectiveness of Athlon's IPO, these shares were subject to an adjustment based on Athlon's IPO price of $20.00 per share and an actual 65.266-for-1 stock split resulting in 66,339,615 shares of Athlon's common stock to be outstanding prior to the closing of the IPO.

	As discussed in "Note 1. Formation of the Company and Description of Business", on August 7, 2013, Athlon completed its IPO of 15,789,474 shares of its common stock at $20.00 per share and received net proceeds of approximately $295.7 million, after deducting underwriting discounts and commissions and offering expenses. Athlon used the net proceeds from the IPO (i) to reduce outstanding borrowings under the Credit Agreement, (ii) to provide additional liquidity for use in its drilling program, and (iii) for general corporate purposes. Upon consummation of the IPO, Athlon's ownership percentage of Holdings increased, resulting in a decrease in the noncontrolling interest from approximately 3.2% to approximately 2.2%.

	Preferred Stock

	Athlon's authorized capital stock includes 50,000,000 shares of preferred stock, none of which were issued and outstanding at December 31, 2013. Athlon does not plan to issue any shares of preferred stock.

Taxes

Taxes	12 Months Ended
Taxes	Dec. 31, 2013
Taxes	'
Taxes	'

	Note 8. Taxes

	Income Taxes

	As a result of the corporate reorganization on April 26, 2013, Athlon (a C-corporation) obtained most of the interests in Holdings. Prior to April 26, 2013, Holdings, Athlon's accounting predecessor, was a limited partnership not subject to federal income taxes.

	The components of income tax provision were as follows for the periods indicated:


			Year Ended December 31,
			2013			2012		2011
			(in thousands)
	Federal:
	Current		$	1,135		$	—	$	—
	Deferred			17,022			—		—


	Total federal			18,157			—		—


	State, net of federal benefit:
	Deferred			993			1,928		470


	Total state			993			1,928		470


	Income tax provision		$	19,150		$	1,928	$	470





	The following table reconciles income tax provision with income tax at the Federal statutory rate for the periods indicated:


			Year Ended December 31,
			2013			2012		2011
			(in thousands)
	Income (loss) before income taxes		$	79,572		$	54,942	$	(659	)
	Less: net income prior to corporate reorganization			(27,320	)		—		—
	Less: net income attributable to noncontrolling interest			(1,359	)		—		—


	Income (loss) before income taxes and noncontrolling interest subsequent to corporate reorganization		$	50,893		$	54,942	$	(659	)




	Income taxes at the Federal statutory rate		$	17,813		$	—	$	—
	State income taxes, net of federal benefit			933			549		21
	Provision to return adjustment			59			—		—
	Permanent and other			345			1,379		449


	Income tax provision		$	19,150		$	1,928	$	470





	The major components of net current deferred taxes and net long-term deferred taxes were as follows as of the dates indicated:


		December 31,
		2013			2012
		(in thousands)
Current:
Assets:
Derivative fair value loss		$	480		$	—


Total current deferred tax assets			480			—


Liabilities:
Prepaid insurance			(100	)		(8	)
Derivative fair value gain			—			(50	)


Total current deferred tax liabilities			(100	)		(58	)


Net current deferred tax asset (liability)		$	380		$	(58	)




Long-term:
Assets:
Alternative minimum tax credits		$	1,135		$	—
Derivative fair value loss			2,080			60
Net operating loss carryforward			43,164			—
Asset retirement obligations			519			8
Deferred equity-based compensation			1,406			—
Acquisition costs capitalized			3,351			95
Other			1,840			25


Total long-term deferred tax assets			53,495			188


Liabilities:
Book basis of oil and natural gas properties in excess of tax basis			(145,892	)		(2,528	)


Total long-term deferred tax liabilities			(145,892	)		(2,528	)


Net long-term deferred tax liability		$	(92,397	)	$	(2,340	)





At December 31, 2013, Athlon had federal net operating loss ("NOL") carryforwards, which are available to offset future federal state taxable income, if any. At December 31, 2013, Athlon also had federal alternative minimum tax ("AMT") credits, which are available to reduce future federal regular tax liabilities in excess of AMT. Athlon believes it is more likely than not that the NOL carryforwards will offset future taxable income prior to their expiration. The AMT credits have no expiration. Therefore, a valuation allowance against these deferred tax assets is not considered necessary. If unused, these carryforwards and credits will expire as follows:


Expiration Date		Federal			Federal
Expiration Date		AMT Credits			NOL
		(in thousands)
2031		$	—		$	2,433
2032			—			77,749
2033			—			43,143
Indefinite			1,135			—


		$	1,135		$	123,325





During 2013, 2012, and 2011, Athlon did not have any interest assessed by the taxing authorities or incur any penalties related to income taxes.

Earnings_Per_Share

Earnings Per Share	12 Months Ended
Earnings Per Share	Dec. 31, 2013
Earnings Per Share	'
Earnings Per Share	'

	Note 9. Earnings Per Share

	Prior to the consummation of Athlon's IPO, Athlon had 960,907 shares of outstanding common stock. In conjunction with the closing of the IPO, certain Class A limited partners and Class B limited partners of Holdings that exchanged their interests for shares of Athlon's common stock were subject to an adjustment based on Athlon's IPO price of $20.00 per share and an actual 65.266-for-1 stock split. Following this adjustment and stock split, the number of outstanding shares of Athlon's common stock increased from 960,907 shares to 66,339,615 shares. The one-to-one conversion of the Holdings' interests in April 2013 to 960,907 shares of Athlon common stock is akin to a stock split and has been treated as such in Athlon's EPS calculations. Accordingly, Athlon assumes that 66,339,615 shares of common stock were outstanding during periods prior to Athlon's IPO for purposes of calculating EPS.

	The following table reflects the allocation of net income (loss) attributable to stockholders and EPS computations for the periods indicated:


		Year ended December 31,
		2013			2012		2011
		(in thousands,
		except per share amounts)
	Basic EPS
	Numerator:
	Undistributed net income (loss) attributable to stockholders	$	59,063		$	53,014	$	(1,129	)
	Participation rights of unvested RSUs in undistributed earnings		(628	)		—		—


	Basic undistributed net income (loss) attributable to stockholders	$	58,435		$	53,014	$	(1,129	)




	Denominator:
	Basic weighted average shares outstanding		72,915			66,340		66,340




	Basic EPS attributable to stockholders	$	0.8		$	0.8	$	(0.02	)




	Diluted EPS
	Numerator:
	Undistributed net income (loss) attributable to stockholders	$	59,063		$	53,014	$	(1,129	)
	Participation rights of unvested RSUs in undistributed earnings		(613	)		—		—
	Effect of conversion of New Holdings Units to shares of Athlon's common stock		1,359			—		—


	Diluted undistributed net income (loss) attributable to stockholders	$	59,809		$	53,014	$	(1,129	)




	Denominator:
	Basic weighted average shares outstanding		72,915			66,340		66,340
	Effect of conversion of New Holdings Units to shares of Athlon's common stock(a)		1,856			1,856		—


	Diluted weighted average shares outstanding		74,771			68,196		66,340




	Diluted EPS attributable to stockholders	$	0.8		$	0.78	$	(0.02	)






(a)
For 2011, 1,855,563 New Holdings Units were outstanding but excluded from the EPS calculations because their effect would have been antidilutive.

Employment_Benefit_Plans

Employment Benefit Plans

12 Months Ended

Dec. 31, 2013

Employment Benefit Plans

Note 10. Employment Benefit Plans

401(k) Plan

Athlon made contributions to its 401(k) plan, which is a voluntary and contributory plan for eligible employees based on a percentage of employee contributions, of $585,000, $454,000, and $219,000 during 2013, 2012, and 2011, respectively. Athlon's 401(k) plan does not allow employees to invest in securities of Athlon.

Incentive Award Plan

In August 2013, Athlon adopted the Athlon Energy Inc. 2013 Incentive Award Plan (the "Plan"). The principal purpose of the Plan is to attract, retain, and engage selected employees, consultants, and directors through the granting of equity and equity-based compensation awards. Employees, consultants, and directors of Athlon and its subsidiaries are eligible to receive awards under the Plan. The Compensation Committee will administer the Plan unless the Board of Directors assumes direct authority for administration. The Plan provides for the grant of stock options (including non-qualified stock options and incentive stock options), restricted stock, dividend equivalents, stock payments, restricted stock units ("RSUs"), performance awards, stock appreciation rights, and other equity-based and cash-based awards, or any combination thereof.

The aggregate number of shares of common stock available for issuance pursuant to awards granted under the Plan is the sum of 8,400,000 shares, subject to adjustment as described below plus an annual increase on the first day of each calendar year beginning January 1, 2014 and ending on and including the last January 1 prior to the expiration date of the Plan, equal to the least of (i) 12,000,000 shares, (ii) 4% of the shares outstanding (on an as-converted basis) on the final day of the immediately preceding calendar year, and (iii) such smaller number of shares as determined by the Board of Directors. This number will also be adjusted due to the following shares becoming eligible to be used again for grants under the Plan:

•

shares subject to awards or portions of awards granted under the Plan which are forfeited, expire, or lapse for any reason, or are settled for cash without the delivery of shares, to the extent of such forfeiture, expiration, lapse, or cash settlement; and

•

shares that Athlon repurchases prior to vesting so that such shares are returned to Athlon.

The Plan does not provide for individual limits on awards that may be granted to any individual participant under the Plan. Rather, the amount of awards to be granted to individual participants are determined by the Board of Directors or the Compensation Committee from time to time, as part of their compensation decision-making processes, provided, however, that the Plan does not permit awards having a grant date fair value in excess of $700,000 to be granted to Athlon's non-employee directors in any year.

As of December 31, 2013, there were 7,761,087 shares available for issuance under the Plan. During 2013, Athlon recorded non-cash stock-based compensation expense related to the Plan of $4.0 million, which was allocated to lease operating expense and general and administrative expense in the accompanying Consolidated Statements of Operations based on the allocation of the respective employees' compensation. During 2013, Athlon also capitalized $263,000 of non-cash stock-based compensation expense related to the Plan as a component of "Evaluated, including wells and related equipment" in the accompanying Consolidated Balance Sheets.

RSUs vest over three years, subject to the relative performance of Athlon's stock to that of a designated peer group for Athlon's management team. The following table summarizes the changes in Athlon's unvested RSUs for 2013 (presented at the target level):

Number of

Weighted-Average

Grant Date

Fair Value

Per Share

Outstanding at January 1

—

Granted

638,913

34.88

Vested

—

Forfeited

—

Outstanding at December 31

638,913

34.88

During 2013, Athlon issued 411,413 RSUs to employees and non-employee directors, the vesting of which is dependent only on the passage of time and continued employment. The following table provides information regarding Athlon's outstanding RSUs at December 31, 2013 the vesting of which is dependent only on the passage of time and continued employment:

Year of Vesting

Year of Grant

2014

2015

2016

Total

2013

137,138

137,137

411,413

During 2013, Athlon also issued 227,500 RSUs to Athlon's management team, the vesting of which is dependent not only on the passage of time and continued employment, but also on the relative performance of Athlon's stock to that of a designated peer group. One-half of the maximum number of shares that could be earned under the performance-based awards will be earned for performance at the designated target levels (100% target vesting levels) or upon any earlier change of control, and twice the number of shares will be earned if the higher maximum target levels are met. If performance is below the designated minimum levels for all performance targets, no performance-based shares will be earned. Performance-based awards were valued using a Monte Carlo simulation. The following table provides information regarding Athlon's outstanding RSUs at December 31, 2013 (presented at the target level) the vesting of which is dependent not only on the passage of time and continued employment, but also on the relative performance of Athlon's stock to that of a designated peer group:

Year of Vesting

Year of Grant

2014

2015

2016

Total

2013

75,834

75,833

227,500

None of Athlon's unvested RSUs are subject to variable accounting. As of December 31, 2013, Athlon had approximately $16.6 million of total unrecognized compensation cost related to unvested RSUs, which is expected to be recognized over a weighted-average period of approximately 2.6 years.

Class B Interests

Holdings' limited partnership agreement provided for the issuance of Class B limited partner interests. As discussed in "Note 1. Formation of the Company and Description of Business", in connection with the corporate reorganization, the holders of the Class B limited partner interests in Holdings exchanged their interests for common stock of Athlon subject to the same conditions and vesting terms. Upon the consummation of Athlon's IPO, the remaining unvested common stock awards, which were formerly Class B interests in Holdings, vested and Athlon recognized non-cash equity-based compensation expense of approximately $1.5 million.

During 2013, 2012, and 2011, Athlon recorded approximately $1.3 million, $152,000, and $106,000, respectively, of non-cash equity-based compensation expense related to Class B interests, which was allocated to lease operating expense and general and administrative expenses in the accompanying Consolidated Statements of Operations based on the allocation of the respective employees' compensation. During 2013 and 2012, Athlon capitalized approximately $415,000 and $93,000, respectively, of non-cash stock-based compensation expense as a component of "Evaluated, including wells and related equipment" in the accompanying Consolidated Balance Sheets.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2013
Commitments and Contingencies	'
Commitments and Contingencies	'

	Note 11. Commitments and Contingencies

	Leases

	Athlon leases certain office space that has non-cancelable lease terms in excess of one year. The following table summarizes the remaining non-cancelable future payments under these operating leases as of December 31, 2013:


		Payments Due by Period
		Total		2014		2015		2016		2017		2018		Thereafter
		(in thousands)
	Corporate office lease	$	1,031	$	375	$	375	$	281	$	—	$	—	$	—
	Midland office lease		285		92		96		97		—		—		—


	Total	$	1,316	$	467	$	471	$	378	$	—	$	—	$	—





	Athlon's operating lease rental expense was approximately $490,000, $507,000, and $272,000 during 2013, 2012, and 2011, respectively.

	Litigation

	From time to time, Athlon is a party to ongoing legal proceedings in the ordinary course of business, including workers' compensation claims and employment-related disputes. Management does not believe the results of these proceedings, individually or in the aggregate, will have a material adverse effect on Athlon's business, financial position, results of operations, or liquidity.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2013
Related Party Transactions	'
Related Party Transactions	'

	Note 12. Related Party Transactions

	Transaction Fee Agreement

	Athlon was a party to a Transaction Fee Agreement, dated August 23, 2010, which required it to pay a fee to Apollo equal to 2% of the total equity contributed to Athlon, as defined in the agreement, in exchange for consulting and advisory services provided by Apollo. In October 2012, Apollo assigned its rights and obligations under the Transaction Fee Agreement to an affiliate, Apollo Global Securities, LLC. Upon the consummation of Athlon's IPO, the Transaction Fee Agreement was terminated. Since Athlon's inception through the termination of the Transaction Fee Agreement, it incurred transaction fees under the Transaction Fee Agreement of approximately $7.5 million in total.

	Services Agreement

	Athlon was a party to a Services Agreement, dated August 23, 2010, which required it to compensate Apollo for consulting and advisory services equal to the higher of (i) 1% of earnings before interest, income taxes, DD&A, and exploration expense per quarter and (ii) $62,500 per quarter (the "Advisory Fee"); provided, however, that such Advisory Fee for any calendar year shall not exceed $500,000. The Services Agreement also provided for reimbursement to Apollo for any reasonable out-of-pocket expenses incurred while performing services under the Services Agreement. During 2013, 2012, and 2011, Athlon incurred approximately $500,000, $493,000, and $411,000, respectively, of Advisory Fees, which are included in "General and administrative expenses" in the accompanying Consolidated Statements of Operations.

	Upon the consummation of Athlon's IPO, the Services Agreement was terminated and Athlon paid a termination fee of $2.4 million (plus $132,000 of unreimbursed fees) to Apollo. Such payment corresponded to the present value as of the date of termination of the aggregate annual fees that would have been payable during the remainder of the term of the Services Agreement (assuming a term ending on August 23, 2020). Under the Services Agreement, Athlon also agreed to indemnify Apollo and its affiliates and their respective limited partners, general partners, directors, members, officers, managers, employees, agents, advisors, and representatives for potential losses relating to the services contemplated under the Services Agreement.

	Participation of Apollo Global Securities, LLC in Senior Notes Offering and IPO

	Apollo Global Securities, LLC is an affiliate of the Apollo Funds and received a portion of the gross spread as an initial purchaser of the Notes of $0.5 million. Apollo Global Securities, LLC was also an underwriter in Athlon's IPO and received a portion of the discounts and commissions paid to the underwriters in the IPO of approximately $0.9 million.

	Distribution

	Athlon used a portion of the net proceeds from the Notes to make a distribution to Holdings' Class A limited partners, including the Apollo Funds and Athlon's management team and certain employees. The Apollo Funds received approximately $73 million of the distribution and Athlon's management team and certain employees received approximately $2 million, in the aggregate.

	Exchange Agreement

	Upon the consummation of its IPO, Athlon entered into an exchange agreement with its management team and certain employees who hold New Holdings Units. Under the exchange agreement, each such holder (and certain permitted transferees thereof) may, under certain circumstances after the date of the closing of the IPO (subject to the terms of the exchange agreement), exchange their New Holdings Units for shares of Athlon's common stock on a one-for-one basis, subject to customary conversion rate adjustments for stock splits, stock dividends, and reclassifications. As a holder exchanges its New Holdings Units, Athlon's interest in Holdings will be correspondingly increased.

	Tax Receivable Agreement

	Upon the consummation of its IPO, Athlon entered into a tax receivable agreement with its management team and certain employees who hold New Holdings Units that provides for the payment from time to time by Athlon to such unitholders of Holdings of 85% of the amount of the benefits, if any, that Athlon is deemed to realize as a result of increases in tax basis and certain other tax benefits related to exchanges of New Holdings Units pursuant to the exchange agreement, including tax benefits attributable to payments under the tax receivable agreement. These payment obligations are obligations of Athlon and not of Holdings. For purposes of the tax receivable agreement, the benefit deemed realized by Athlon will be computed by comparing its actual income tax liability (calculated with certain assumptions) to the amount of such taxes that Athlon would have been required to pay had there been no increase to the tax basis of the assets of Holdings as a result of the exchanges and had Athlon not entered into the tax receivable agreement.

	The step-up in basis will depend on the fair value of the New Holdings Units at conversion. There is no intent of the holders of New Holdings Units to exchange their units for shares of Athlon's common stock in the foreseeable future. In addition, Athlon does not expect to be in a tax paying position before 2019. Therefore, Athlon cannot presently estimate what the benefit or payments under the tax receivable agreement will be on a factually supportable basis, and accordingly not recognized as a liability.

Subsequent_Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2013
Subsequent Events	'
Subsequent Events	'

	Note 13. Subsequent Events

	Subsequent to December 31, 2013, Athlon entered into additional oil swaps. The following table summarizes Athlon's open commodity derivative contracts as of March 7, 2014:


	Period	Average		Weighted-Average
		Daily Swap		Swap Price
		Volume
		(Bbl)		(per Bbl)
	Q1 2014		8,606	$	92.7
	Q2 2014		8,950		92.71
	Q3 2014		9,950		92.52
	Q4 2014		9,950		92.52
	2014		9,369		92.61
	Q1 2015		4,300		91.29
	Q2 2015		4,300		91.29
	Q3 2015		1,300		93.18
	Q4 2015		1,300		93.18
	2015		2,788		91.74

	On February 6, 2014, Athlon completed the acquisition of certain oil and natural gas properties and related assets in the Midland Basin of West Texas for approximately $88 million in cash (subject to customary post-closing adjustments), pursuant to a Purchase and Sale Agreement dated January 10, 2014 with an effective date of September 1, 2013. Athlon also agreed to acquire additional working interests in the properties, partially offset by the exercise of certain preferential rights, with the net effect of an $8.7 million purchase price increase. The acquisition was financed through cash on hand and borrowings under the Credit Agreement.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2013

Summary of Significant Accounting Policies

Principles of Consolidation

Athlon's consolidated financial statements include the accounts of its wholly owned and majority-owned subsidiaries. All material intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

Preparing financial statements in conformity with accounting principles generally accepted in the United States requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses, and the disclosure of contingent assets and liabilities in the consolidated financial statements. Although management believes these estimates are reasonable, actual results could differ materially from those estimates.

Estimates made in preparing these consolidated financial statements include, among other things, estimates of the proved oil and natural gas reserve volumes used in calculating depletion, depreciation, and amortization ("DD&A") expense; operating costs accrued; volumes and prices for revenues accrued; valuation of derivative instruments; and the timing and amount of future abandonment costs used in calculating asset retirement obligations. Changes in the assumptions used could have a significant impact on results in future periods.

Cash and Cash Equivalents

Cash and cash equivalents include demand deposits and funds invested in highly liquid instruments with original maturities of three months or less and typically exceed federally insured limits.

The following table sets forth supplemental disclosures of cash flow information for the periods indicated:

Year ended December 31,

2013

2012

2011

(in thousands)

Cash paid during the period for:

Interest

25,220

8,326

2,395

Income taxes

—

Accounts Receivable

Accounts receivable, which are primarily from the sale of oil, natural gas, and natural gas liquids ("NGLs"), is accrued based on estimates of the sales and prices Athlon believes it will receive. Athlon routinely reviews outstanding balances, assesses the financial strength of its customers, and records a reserve for amounts not expected to be fully recovered. Actual balances are not applied against the reserve until substantially all collection efforts have been exhausted. At December 31, 2013 and 2012, Athlon did not have an allowance for doubtful accounts.

Inventory

Inventory includes materials and supplies that Athlon intends to deploy to various development activities and oil in tanks at the lease, both of which are stated at the lower of cost (determined on an average basis) or market. Oil in tanks at the lease is carried at an amount equal to its costs to produce. Inventory consisted of the following as of the dates indicated:

December 31,

2013

2012

(in thousands)

Materials and supplies

429

670

Oil inventory

499

352

Total inventory

928

1,022

Oil and Natural Gas Properties

Athlon applies the provisions of the "Extractive Activities—Oil and Gas" topic of the Financial Accounting Standards Board's (the "FASB") Accounting Standards Codification (the "ASC"). Athlon uses the full cost method of accounting for its oil and natural gas properties. Under this method, costs directly associated with the acquisition, exploration, and development of reserves are capitalized into a full cost pool. Capitalized costs are amortized using a unit-of-production method. Under this method, the provision for DD&A is computed at the end of each period by multiplying total production for the period by a depletion rate. The depletion rate is determined by dividing the total unamortized cost base plus future development costs by net equivalent proved reserves at the beginning of the period.

Costs associated with unevaluated properties are excluded from the amortizable cost base until a determination has been made as to the existence of proved reserves. Unevaluated properties are reviewed at the end of each quarter to determine whether the costs incurred should be reclassified to the full cost pool and, thereby, subjected to amortization. The costs associated with unevaluated properties primarily consist of acquisition and leasehold costs as well as development costs for wells in progress for which a determination of the existence of proved reserves has not been made. These costs are transferred to the amortization base once a determination is made whether or not proved reserves can be assigned to the property, upon impairment of a lease, or immediately upon determination that the well is unsuccessful. Costs of seismic data that cannot be directly associated to specific properties are included in the full cost pool as incurred; otherwise, they are allocated to various unevaluated leaseholds and transferred to the amortization base with the associated leasehold costs on a specific project basis.

Independent petroleum engineers estimate Athlon's proved reserves annually as of December 31. This results in a new DD&A rate which Athlon uses for the preceding fourth quarter after adjusting for fourth quarter production. Athlon internally estimates reserve additions and reclassifications of reserves from unproved to proved at the end of the first, second, and third quarters for use in determining a DD&A rate for the respective quarter.

Sales and abandonments of oil and natural gas properties being amortized are accounted for as adjustments to the full cost pool, with no gain or loss recognized, unless the adjustments would significantly alter the relationship between capitalized costs and proved reserves. A significant alteration would not ordinarily be expected to occur upon the sale of reserves involving less than 25% of the reserve quantities of a cost center.

Natural gas volumes are converted to barrels of oil equivalent ("BOE") at the rate of six thousand cubic feet ("Mcf") of natural gas to one barrel ("Bbl") of oil. This convention is not an equivalent price basis and there may be a large difference in value between an equivalent volume of oil versus an equivalent volume of natural gas.

Athlon capitalizes interest on expenditures made in connection with exploratory projects that are not subject to current amortization. Interest is capitalized only for the period that activities are in progress to bring these projects to their intended use. Capitalized interest cannot exceed gross interest expense. During 2013 and 2012, Athlon capitalized approximately $0.3 million and $0.2 million, respectively, of interest expense. During 2011, Athlon did not capitalize any interest expense.

Unevaluated properties are assessed periodically, at least annually, for possible impairment. Properties are assessed on an individual basis or as a group if properties are individually insignificant. The assessment includes consideration of various factors, including, but not limited to: intent to drill, remaining lease term, geological and geophysical evaluations, drilling results, and economic viability of development if proved reserves are assigned. During any period in which these factors indicate impairment, the cumulative drilling costs incurred to date for such property and all or a portion of the associated leasehold costs are transferred to the full cost pool and become subject to amortization.

Under the full cost method of accounting, total capitalized costs of oil and natural gas properties, net of accumulated DD&A, less related deferred income taxes may not exceed an amount equal to the present value of future net revenues from proved reserves, discounted at 10% per annum, plus the lower of cost or fair value of unevaluated properties, plus estimated salvage value, less the related tax effects (the "ceiling limitation"). A ceiling limitation is calculated at the end of each quarter. If total capitalized costs, net of accumulated DD&A, less related deferred income taxes are greater than the ceiling limitation, a write-down or impairment of the full cost pool is required. A write-down of the carrying value of the full cost pool is a non-cash charge that reduces earnings and impacts equity in the period of occurrence and typically results in lower DD&A expense in future periods. Once incurred, a write-down cannot be reversed at a later date.

The ceiling limitation calculation is prepared using the 12-month first-day-of-the-month oil and natural gas average prices, as adjusted for basis or location differentials, held constant over the life of the reserves ("net wellhead prices"). If applicable, these net wellhead prices would be further adjusted to include the effects of any fixed price arrangements for the sale of oil and natural gas. Athlon uses commodity derivative contracts to mitigate the risk against the volatility of oil and natural gas prices. Commodity derivative contracts that qualify and are designated as cash flow hedges are included in estimated future cash flows. Athlon has not designated any of its commodity derivative contracts as cash flow hedges and therefore has excluded commodity derivative contracts in estimating future cash flows. The future cash outflows associated with future development or abandonment of wells are included in the computation of the discounted present value of future net revenues for purposes of the ceiling limitation calculation.

Amounts shown in the accompanying Consolidated Balance Sheets as "Evaluated, including wells and related equipment" consisted of the following as of the dates indicated:

December 31,

2013

2012

(in thousands)

Evalauted leasehold costs

448,689

376,271

Wells and related equipment—completed

748,900

379,036

Wells and related equipment—in process

46,589

33,264

Total evaluated

1,244,178

788,571

Asset Retirement Obligations

Athlon applies the provisions of the "Asset Retirement and Environmental Obligations" topic of the ASC. Athlon has obligations as a result of lease agreements and enacted laws to remove its equipment and restore land at the end of production operations. These asset retirement obligations are primarily associated with plugging and abandoning wells and land remediation. At the time a drilled well is completing or a well is acquired, Athlon records a separate liability for the estimated fair value of its asset retirement obligations, with an offsetting increase to the related oil and natural gas asset representing asset retirement costs in the accompanying Consolidated Balance Sheets. The cost of the related oil and natural gas asset, including the asset retirement cost, is included in Athlon's full cost pool. The estimated fair value of an asset retirement obligation is the present value of the expected future cash outflows required to satisfy the asset retirement obligations discounted at Athlon's credit-adjusted, risk-free interest rate at the time the liability is incurred. Accretion expense is recognized over time as the discounted liability is accreted to its expected settlement value.

Inherent to the present-value calculation are numerous estimates, assumptions, and judgments, including, but not limited to: the ultimate settlement amounts, inflation factors, credit-adjusted risk-free rates, timing of settlement, and changes in the legal, regulatory, environmental, and political environments. To the extent future revisions to these assumptions affect the present value of the abandonment liability, Athlon makes corresponding adjustments to both the asset retirement obligation and the related oil and natural gas property asset balance. These revisions result in prospective changes to DD&A expense and accretion of the discounted abandonment liability. Please read "Note 5. Asset Retirement Obligations" for additional information.

Equity-Based Compensation

Athlon accounts for equity-based compensation according to the "Share-Based Payment" topic of the ASC, which requires the recognition of compensation expense for equity-based awards over the requisite service period in an amount equal to the grant date fair value of the awards. Please read "Note 9. Employee Benefit Plans" for additional discussion of Athlon's employee benefit plans.

The "Share-Based Payment" topic of the ASC also requires that the benefits associated with the tax deductions in excess of recognized compensation cost, if any, be reported as a financing cash flow. This requirement reduces net operating cash flows and increases net financing cash flows. Athlon recognizes compensation costs related to awards with graded vesting on a straight-line basis over the requisite service period for each separately vesting portion of the award as if the award was, in substance, multiple awards.

Segment Reporting

Athlon only operates in the oil and natural gas exploration and production industry in the United States. All revenues are derived from customers located in the United States.

Major Customers / Concentration of Credit Risk

The following purchasers accounted for 10% or greater of the sales of production for the periods indicated and the corresponding outstanding accounts receivable balance as of the dates indicated:

Percentage of Total

Outstanding

Revenues for

Accounts

the Year Ended

Receivable Balance

December 31,

as of December 31,

Purchaser

2013

2012

2011

2013

2012

(in thousands)

Occidental Petroleum Corporation

11,673

4,456

DCP Midstream

(a)

2,604

High Sierra Crude Oil & Marketing, LLC(b)

18,951

9,348

(a)

Less than 10% for the period indicated.

(b)

Formerly Pecos Gathering & Marketing.

Income Taxes

Athlon accounts for income taxes using the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax laws and rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.

Athlon periodically assesses whether it is more likely than not that it will generate sufficient taxable income to realize its deferred income tax assets, including net operating losses. In making this determination, Athlon considers all available positive and negative evidence and makes certain assumptions. Athlon considers, among other things, its deferred tax liabilities, the overall business environment, its historical earnings and losses, current industry trends, and its outlook for future years. Athlon believes it is more likely than not that certain net operating losses can be carried forward and utilized.

In April 2013, Athlon effected a corporate reorganization. Holdings, Athlon's accounting predecessor, is a partnership not subject to federal income tax. Pursuant to the corporate reorganization, certain Class A limited partners and the Class B limited partners of Holdings exchanged their interests for shares of Athlon's common stock. Athlon's operations are now subject to federal income tax. The tax implications of the corporate reorganization and the tax impact of the conversion to operating as a taxable entity have been reflected in the accompanying consolidated financial statements.

Revenue Recognition

Revenues from the sale of oil, natural gas, and NGLs are recognized when they are realized or realizable and earned. Revenues are considered realized or realizable and earned when: (i) persuasive evidence of an arrangement exists; (ii) delivery has occurred or services have been rendered; (iii) the seller's price to the buyer is fixed or determinable; and (iv) collectability is reasonably assured. Because final settlement of our hydrocarbon sales can take up to two months, sales volumes and prices are estimated and accrued using information available at the time the revenue is recorded. If Athlon's overproduced imbalance position (i.e., Athlon has cumulatively been over-allocated production) is greater than its share of remaining reserves, a liability would be recorded for the excess at period-end prices unless a different price is specified in the contract, in which case that price is used. At December 31, 2013 and 2012, Athlon did not have any natural gas imbalances. Revenue is not recognized for oil production in tanks, but the production is recorded as a current asset based on the cost to produce and included in "Inventory" in the accompanying Consolidated Balance Sheets. Transportation expenses are included in operating expenses and are insignificant.

Derivatives

Athlon uses various financial instruments for non-trading purposes to manage and reduce price volatility and other market risks associated with its oil production. These arrangements are structured to reduce Athlon's exposure to commodity price decreases, but they can also limit the benefit Athlon might otherwise receive from commodity price increases. Athlon's risk management activity is generally accomplished through over-the-counter commodity derivative contracts with large financial institutions, most of which are lenders under Athlon's credit agreement.

Athlon applies the provisions of the "Derivatives and Hedging" topic of the ASC, which requires each derivative instrument to be recorded in the accompanying Consolidated Balance Sheets at fair value. If a derivative has not been designated as a hedge or does not otherwise qualify for hedge accounting, it must be adjusted to fair value through earnings. Athlon elected not to designate its current portfolio of commodity derivative contracts as hedges for accounting purposes. Therefore, changes in fair value of these derivative instruments are recognized in earnings and included in "Derivative fair value loss (gain)" in the accompanying Consolidated Statements of Operations.

Athlon enters into commodity derivative contracts for the purpose of economically fixing the price of its anticipated oil production even though Athlon does not designate the derivatives as hedges for accounting purposes. Athlon classifies cash flows related to derivative contracts based on the nature and purpose of the derivative. As the derivative cash flows are considered an integral part of Athlon's oil and natural gas operations, they are classified as cash flows from operating activities in the accompanying Consolidated Statements of Cash Flows.

Noncontrolling Interest

As of December 31, 2013, management and certain employees owned approximately 2.2% of Holdings. Athlon owns 100% of Athlon Holdings GP LLC, which is Holdings' general partner. Considering the presumption of control, Athlon has fully consolidated the financial position, results of operations, and cash flows of Holdings.

As presented in the accompanying Consolidated Balance Sheets, "Noncontrolling interest" as of December 31, 2013 of approximately $10.8 million represents management and certain employees' 1,855,563 New Holdings Units that are exchangeable for shares of Athlon's common stock on a one-for-one basis. As presented in the accompanying Consolidated Statements of Operations, "Net income attributable to noncontrolling interest" for 2013 of approximately $1.4 million represents the net income of Holdings attributable to management and certain employees since April 26, 2013.

The following table summarizes the effects of changes in Athlon's partnership interest in Holdings on Athlon's equity for 2013 (in thousands):

Net income attributable to stockholders

59,063

Transfer from noncontrolling interest:

Increase in Athlon's paid-in capital for corporate reorganization

292,549

Increase in Athlon's paid-in capital for issuance of 15,789,474 shares of common stock in initial public offering

295,498

Net transfer from noncontrolling interest

588,047

Change from net income attributable to stockholders and transfers from noncontrolling interest

647,110

Earnings Per Share

For purposes of calculating earnings per share ("EPS"), Athlon allocates net income (loss) to its shareholders and participating securities each quarter under the provisions of the "Earnings Per Share" topic of the ASC. Under the two-class method of calculating EPS, earnings are allocated to participating securities as if all the earnings for the period had been distributed. A participating security is any security that may participate in distributions with common shares. For purposes of calculating EPS, unvested restricted stock units are considered participating securities. Net income (loss) per common share is calculated by dividing the shareholders' interest in net income (loss), after deducting the interests of participating securities, by the weighted average common shares outstanding.

New Accounting Pronouncements

In December 2011, the FASB issued Accounting Standards Update ("ASU") 2011-11, "Disclosures about Offsetting Assets and Liabilities" and in January 2013 issued ASU 2013-01, "Clarifying the Scope of Disclosures About Offsetting Assets and Liabilities". These ASUs created new disclosure requirements regarding the nature of an entity's rights of offset and related arrangements associated with its derivative instruments, repurchase agreements, and securities lending transactions. Certain disclosures of the amounts of certain instruments subject to enforceable master netting arrangements are required, irrespective of whether the entity has elected to offset those instruments in the statement of financial position. These ASUs were effective retrospectively for annual reporting periods beginning on or after January 1, 2013. The adoption of these ASUs did not impact Athlon's financial position, results of operations, or liquidity.

No other new accounting pronouncements issued or effective from January 1, 2013 through the date of this Report, had or are expected to have a material impact on Athlon's consolidated financial statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
Summary of Significant Accounting Policies (Tables)	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Schedule of supplemental disclosures of cash flow information	'




		Year ended December 31,
		2013			2012			2011
		(in thousands)
	Cash paid during the period for:
	Interest	$	25,220		$	8,326		$	2,395
	Income taxes		—			—			—
Schedule of inventory	'




		December 31,
		2013			2012
		(in thousands)
	Materials and supplies	$	429		$	670
	Oil inventory		499			352


	Total inventory	$	928		$	1,022




Schedule of evaluated properties, including wells and related equipment	'




		December 31,
		2013			2012
		(in thousands)
	Evalauted leasehold costs	$	448,689		$	376,271
	Wells and related equipment—completed		748,900			379,036
	Wells and related equipment—in process		46,589			33,264


	Total evaluated	$	1,244,178		$	788,571




Schedule of major customers outstanding accounts receivable balance	'




		Percentage of Total									Outstanding
		Revenues for									Accounts
		the Year Ended									Receivable Balance
		December 31,									as of December 31,
	Purchaser	2013			2012			2011			2013			2012
											(in thousands)
	Occidental Petroleum Corporation		27	%		29	%		58	%	$	11,673		$	4,456
	DCP Midstream			(a)		12	%		13	%			(a)		2,604
	High Sierra Crude Oil & Marketing, LLC(b)		46	%		43	%		13	%		18,951			9,348


	(a)
	Less than 10% for the period indicated.

	(b)
	Formerly Pecos Gathering & Marketing.

Summary of effects of changes in Athlon's partnership interest in Holdings on Athlon's equity	'

	The following table summarizes the effects of changes in Athlon's partnership interest in Holdings on Athlon's equity for 2013 (in thousands):


	Net income attributable to stockholders	$	59,063


	Transfer from noncontrolling interest:
	Increase in Athlon's paid-in capital for corporate reorganization		292,549
	Increase in Athlon's paid-in capital for issuance of 15,789,474 shares of common stock in initial public offering		295,498


	Net transfer from noncontrolling interest		588,047


	Change from net income attributable to stockholders and transfers from noncontrolling interest	$	647,110

Acquisitions_Tables

Acquisitions (Tables)	12 Months Ended
Acquisitions (Tables)	Dec. 31, 2013
Element	'
Acquisitions	'
Schedule of allocation of purchase price to the fair value of assets acquired and liabilities assumed	'

	The allocation of the purchase price to the fair value of the assets acquired and liabilities assumed from Element was as follows (in thousands):


	Proved properties, including wells and related equipment	$	130,527
	Unproved properties		123,107
	Other assets		806


	Total assets acquired		254,440


	Current liabilities		831
	Asset retirement obligations		393


	Total liabilities assumed		1,224


	Fair value of net assets acquired	$	253,216




Schedule of unaudited pro forma condensed financial data	'




		Year ended
		December 31, 2011
		(in thousands, except
		per share amounts)
	Pro forma total revenues	$	89,618




	Pro forma net income attributable to stockholders	$	9,777




	Pro forma net income per common share:
	Basic	$	0.15
	Diluted	$	0.14
SandRidge	'
Acquisitions	'
Schedule of allocation of purchase price to the fair value of assets acquired and liabilities assumed	'

	The allocation of the purchase price to the fair value of the assets acquired and liabilities assumed from SandRidge was as follows (in thousands):


	Proved properties, including wells and related equipment	$	158,157
	Oil inventory		637


	Total assets acquired		158,794
	Asset retirement obligations		2,778


	Fair value of net assets acquired	$	156,016

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2013
Fair Value Measurements	'
Summary of open commodity derivative contracts	'

	Period		Average			Weighted-			Asset
			Daily			Average			(Liability)
			Swap			Swap			Fair Market
			Volume			Price			Value
			(Bbl)			(per Bbl)			(in thousands)
	2014			7,950		$	92.67		$	(8,354	)
	2015			1,300			93.18			2,330


									$	(6,024	)




Schedule of committed 10% or greater (in terms of fair market value) of oil derivative contracts in asset positions from counterparties, or their affiliates	'




	Counterparty		Fair Market Value of
			Oil Derivative
			Contracts
			Committed
			(in thousands)
	BNP Paribas		$	1,082
Schedule of fair value of derivative instruments not designated as hedging instruments	'

	Balance Sheet Location		Oil			Commodity			Total
			Commodity			Derivatives			Commodity
			Derivatives			Netting(a)			Derivatives
			(in thousands)
	As of December 31, 2013
	Assets
	Derivatives—current		$	143		$	(143	)	$	—
	Derivatives—noncurrent			2,330			—			2,330


	Total assets			2,473			(143	)		2,330


	Liabilities
	Derivatives—current			(8,497	)		143			(8,354	)
	Derivatives—noncurrent			—			—			—


	Total liabilities			(8,497	)		143			(8,354	)


	Net liabilities		$	(6,024	)	$	—		$	(6,024	)




	As of December 31, 2012
	Assets
	Derivatives—current		$	3,386		$	(1,140	)	$	2,246
	Derivatives—noncurrent			3,265			(411	)		2,854


	Total assets			6,651			(1,551	)		5,100


	Liabilities
	Derivatives—current			(1,732	)		1,140			(592	)
	Derivatives—noncurrent			(930	)		411			(519	)


	Total liabilities			(2,662	)		1,551			(1,111	)


	Net assets		$	3,989		$	—		$	3,989






	(a)
	Represents counterparty netting under master netting agreements, which allow for netting of commodity derivative contracts. These derivative instruments are reflected net on the accompanying Consolidated Balance Sheets.

Schedule of effect of derivative instruments not designated as hedges on accompanying consolidated statements of operation	'

					Amount of Loss (Gain)
					Recognized in
					Income
					Year ended December 31,
			Location of Loss (Gain)		Year ended December 31,
	Derivatives Not Designated as Hedges		Recognized in Income		2013			2012			2011
					(in thousands)
	Commodity derivative contracts		Derivative fair value loss (gain)		$	18,115		$	(9,293	)	$	7,959
Schedule of assets and liabilities that accounted for at fair value on a recurring basis	'
		Fair Value Measurements at Reporting Date Using
	Description		Net Asset (Liability)			Quoted Prices in			Significant Other			Significant
						Active Markets for			Observable Inputs			Unobservable Inputs
						Identical Assets			(Level 2)			(Level 3)
						(Level 1)
			(in thousands)
	As of December 31, 2013
	Oil derivative contracts—swaps		$	(6,024	)	$	—		$	(6,024	)	$	—
	As of December 31, 2012
	Oil derivative contracts—swaps		$	4,069		$	—		$	4,069		$	—
	Oil derivative contracts—collars			(80	)		—			(80	)		—


	Total		$	3,989		$	—		$	3,989		$	—

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	12 Months Ended
Asset Retirement Obligations (Tables)	Dec. 31, 2013
Asset Retirement Obligations	'
Summary of changes in asset retirement obligations	'
		Year Ended
		December 31,
		2013			2012
		(in thousands)
	Balance at January 1	$	5,049		$	3,704
	Liabilities assumed in acquisitions		395			60
	Liabilities incurred from new wells		1,013			815
	Liabilities settled		(283	)		—
	Accretion of discount		675			478
	Revisions of previous estimates		6			(8	)


	Balance at December 31		6,855			5,049
	Less: current portion		60			—


	Asset retirement obligations—long-term	$	6,795		$	5,049

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2013
Long-Term Debt.	'
Schedule of quarterly commitment fee on unused portion of the Credit Agreement and applicable margin for Eurodollar and base rate loans	'




	Ratio of Outstanding Borrowings to Borrowing Base	Unused			Applicable			Applicable
		Commitment Fee			Margin for			Margin for Base
					Eurodollar Loans			Rate Loans
	Less than or equal to .30 to 1		0.375	%		1.5	%		0.5	%
	Greater than .30 to 1 but less than or equal to .60 to 1		0.375	%		1.75	%		0.75	%
	Greater than .60 to 1 but less than or equal to .80 to 1		0.5	%		2	%		1	%
	Greater than .80 to 1 but less than or equal to .90 to 1		0.5	%		2.25	%		1.25	%
	Greater than .90 to 1		0.5	%		2.5	%		1.5	%
Schedule of long-term debt maturities	'




		Payments Due by Period
		Total			2014			2015			2016		2017		2018		Thereafter
		(in thousands)
	Credit Agreement	$	—		$	—		$	—		$	—	$	—	$	—	$	—
	7³/8% Senior Notes		500,000			—			—			—		—		—		500,000


	Total	$	500,000		$	—		$	—		$	—	$	—	$	—	$	500,000

Taxes_Tables

Taxes (Tables)	12 Months Ended
Taxes (Tables)	Dec. 31, 2013
Taxes	'
Schedule of the components of income tax provision	'




		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Federal:
	Current	$	1,135		$	—		$	—
	Deferred		17,022			—			—


	Total federal		18,157			—			—


	State, net of federal benefit:
	Deferred		993			1,928			470


	Total state		993			1,928			470


	Income tax provision	$	19,150		$	1,928		$	470




Schedule of reconciliation of income tax provision with income tax at the Federal statutory rate	'




		Year Ended December 31,
		2013			2012			2011
		(in thousands)
	Income (loss) before income taxes	$	79,572		$	54,942		$	(659	)
	Less: net income prior to corporate reorganization		(27,320	)		—			—
	Less: net income attributable to noncontrolling interest		(1,359	)		—			—


	Income (loss) before income taxes and noncontrolling interest subsequent to corporate reorganization	$	50,893		$	54,942		$	(659	)




	Income taxes at the Federal statutory rate	$	17,813		$	—		$	—
	State income taxes, net of federal benefit		933			549			21
	Provision to return adjustment		59			—			—
	Permanent and other		345			1,379			449


	Income tax provision	$	19,150		$	1,928		$	470




Schedule of the major components of net current deferred taxes and net long-term deferred taxes	'

		December 31,
		2013			2012
		(in thousands)
	Current:
	Assets:
	Derivative fair value loss	$	480		$	—


	Total current deferred tax assets		480			—


	Liabilities:
	Prepaid insurance		(100	)		(8	)
	Derivative fair value gain		—			(50	)


	Total current deferred tax liabilities		(100	)		(58	)


	Net current deferred tax asset (liability)	$	380		$	(58	)




	Long-term:
	Assets:
	Alternative minimum tax credits	$	1,135		$	—
	Derivative fair value loss		2,080			60
	Net operating loss carryforward		43,164			—
	Asset retirement obligations		519			8
	Deferred equity-based compensation		1,406			—
	Acquisition costs capitalized		3,351			95
	Other		1,840			25


	Total long-term deferred tax assets		53,495			188


	Liabilities:
	Book basis of oil and natural gas properties in excess of tax basis		(145,892	)		(2,528	)


	Total long-term deferred tax liabilities		(145,892	)		(2,528	)


	Net long-term deferred tax liability	$	(92,397	)	$	(2,340	)




Schedule of expiration of carryforwards and credits	'




	Expiration Date	Federal			Federal
	Expiration Date	AMT Credits			NOL
		(in thousands)
	2031	$	—		$	2,433
	2032		—			77,749
	2033		—			43,143
	Indefinite		1,135			—


		$	1,135		$	123,325

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	12 Months Ended
Earnings Per Share (Tables)	Dec. 31, 2013
Earnings Per Share	'
Schedule of allocation of net income (loss) attributable to stockholders and EPS computations	'




		Year ended December 31,
		2013			2012		2011
		(in thousands,
		except per share amounts)
	Basic EPS
	Numerator:
	Undistributed net income (loss) attributable to stockholders	$	59,063		$	53,014	$	(1,129	)
	Participation rights of unvested RSUs in undistributed earnings		(628	)		—		—


	Basic undistributed net income (loss) attributable to stockholders	$	58,435		$	53,014	$	(1,129	)




	Denominator:
	Basic weighted average shares outstanding		72,915			66,340		66,340




	Basic EPS attributable to stockholders	$	0.8		$	0.8	$	(0.02	)




	Diluted EPS
	Numerator:
	Undistributed net income (loss) attributable to stockholders	$	59,063		$	53,014	$	(1,129	)
	Participation rights of unvested RSUs in undistributed earnings		(613	)		—		—
	Effect of conversion of New Holdings Units to shares of Athlon's common stock		1,359			—		—


	Diluted undistributed net income (loss) attributable to stockholders	$	59,809		$	53,014	$	(1,129	)




	Denominator:
	Basic weighted average shares outstanding		72,915			66,340		66,340
	Effect of conversion of New Holdings Units to shares of Athlon's common stock(a)		1,856			1,856		—


	Diluted weighted average shares outstanding		74,771			68,196		66,340




	Diluted EPS attributable to stockholders	$	0.8		$	0.78	$	(0.02	)






	(a)
	For 2011, 1,855,563 New Holdings Units were outstanding but excluded from the EPS calculations because their effect would have been antidilutive.

Employment_Benefit_Plans_Table

Employment Benefit Plans (Tables)	12 Months Ended
Employment Benefit Plans (Tables)	Dec. 31, 2013
Employment Benefit Plans	'
Summary of changes in unvested RSUs	'






		Number of		Weighted-Average
		Shares		Grant Date
				Fair Value
				Per Share
	Outstanding at January 1		—	$	—
	Granted		638,913		34.88
	Vested		—		—
	Forfeited		—		—


	Outstanding at December 31		638,913		34.88




Vesting of awards subject to time and continued employment condition	'
Incentive award plan	'
Schedule of vesting of RSUs	'




		Year of Vesting
	Year of Grant	2014		2015		2016		Total
	2013		137,138		137,138		137,137		411,413
Vesting of awards subject to time, continued employment and performance condition	'
Incentive award plan	'
Schedule of vesting of RSUs	'

		Year of Vesting
	Year of Grant	2014		2015		2016		Total
	2013		75,834		75,833		75,833		227,500

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
Commitments and Contingencies (Tables)	Dec. 31, 2013
Commitments and Contingencies	'
Summary of the remaining non-cancelable future payments under these operating leases	'

		Payments Due by Period
		Total		2014		2015		2016		2017		2018		Thereafter
		(in thousands)
	Corporate office lease	$	1,031	$	375	$	375	$	281	$	—	$	—	$	—
	Midland office lease		285		92		96		97		—		—		—


	Total	$	1,316	$	467	$	471	$	378	$	—	$	—	$	—

Subsequent_Events_Tables

Subsequent Events (Tables)	12 Months Ended
Subsequent Events (Tables)	Dec. 31, 2013
Subsequent events	'
Summary of open commodity derivative contracts	'

	Period	Average		Weighted-		Asset
		Daily		Average		(Liability)
		Swap		Swap		Fair Market
		Volume		Price		Value
		(Bbl)		(per Bbl)		(in thousands)
	2014		7,950	$	92.67	$	(8,354	)
	2015		1,300		93.18		2,330


						$	(6,024	)




Subsequent event	'
Subsequent events	'
Summary of open commodity derivative contracts	'

	The following table summarizes Athlon's open commodity derivative contracts as of March 7, 2014:


	Period	Average		Weighted-Average
		Daily Swap		Swap Price
		Volume
		(Bbl)		(per Bbl)
	Q1 2014		8,606	$	92.7
	Q2 2014		8,950		92.71
	Q3 2014		9,950		92.52
	Q4 2014		9,950		92.52
	2014		9,369		92.61
	Q1 2015		4,300		91.29
	Q2 2015		4,300		91.29
	Q3 2015		1,300		93.18
	Q4 2015		1,300		93.18
	2015		2,788		91.74

Formation_of_the_Company_and_D1

Formation of the Company and Description of Business (Details) (USD $)	0 Months Ended	12 Months Ended
	Aug. 07, 2013	Dec. 31, 2013	Apr. 26, 2013
Formation of the Company and Description of Business	'	'	'
Tax impact of corporate reorganization	'	'	$71,600,000
Initial public offering	'	'	'
Shares of common stock issued in IPO	15,789,474	'	'
Per share price (in dollars per share)	$20	'	'
Net proceeds from IPO, after deducting underwriting discounts and commissions and offering expenses (in dollars)	$295,700,000	$295,697,000	'
Number of common stock exchangeable against each unit	'	1	'
Holdings	'	'	'
Initial public offering	'	'	'
Shares of common stock issued in IPO	'	15,789,474	'
Holdings \| Class A limited partners	'	'	'
Initial public offering	'	'	'
Exchange Agreement Number of New Units Exchangeable Against Limited Partner Interest	1,855,563	'	'
Number of common stock exchangeable against each unit	'	1	'

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash paid during the period for:	'	'	'
Interest	$25,220,000	$8,326,000	$2,395,000
Income taxes	0	0	0
Inventory	'	'	'
Materials and supplies	429,000	670,000	'
Oil inventory	499,000	352,000	'
Total inventory	928,000	1,022,000	'
Oil and Natural Gas Properties	'	'	'
Gain or loss recognized on sales and abandonments of oil and natural gas properties	0	'	'
Minimum percentage of sale of proved reserve quantities for significant alteration	25.00%	'	'
Interest expense capitalized	300,000	200,000	'
Discount rate (as a percent)	10.00%	'	'
Period used in calculation of ceiling limitation	'12 months	'	'
Evaluated, including wells and related equipment	'	'	'
Evaluated leasehold costs	448,689,000	376,271,000	'
Wells and related equipment - completed	748,900,000	379,036,000	'
Wells and related equipment - in process	46,589,000	33,264,000	'
Total evaluated	1,244,178,000	788,571,000	'
Major Customers / Concentration of Credit Risk	'	'	'
Outstanding accounts receivable	48,238,000	24,501,000	'
Revenue Recognition	'	'	'
Maximum period for final settlement of hydrocarbon sales	'2 months	'	'
Revenues \| Purchaser \| Occidental Petroleum Corporation	'	'	'
Major Customers / Concentration of Credit Risk	'	'	'
Percentage of total revenues	27.00%	29.00%	58.00%
Revenues \| Purchaser \| DCP Midstream	'	'	'
Major Customers / Concentration of Credit Risk	'	'	'
Percentage of total revenues	'	12.00%	13.00%
Revenues \| Purchaser \| Pecos Gathering & Marketing	'	'	'
Major Customers / Concentration of Credit Risk	'	'	'
Percentage of total revenues	46.00%	43.00%	13.00%
Accounts Receivable \| Purchaser \| Occidental Petroleum Corporation	'	'	'
Major Customers / Concentration of Credit Risk	'	'	'
Outstanding accounts receivable	11,673,000	4,456,000	'
Accounts Receivable \| Purchaser \| DCP Midstream	'	'	'
Major Customers / Concentration of Credit Risk	'	'	'
Outstanding accounts receivable	'	2,604,000	'
Accounts Receivable \| Purchaser \| Pecos Gathering & Marketing	'	'	'
Major Customers / Concentration of Credit Risk	'	'	'
Outstanding accounts receivable	$18,951,000	$9,348,000	'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Details 2) (USD $)	0 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Aug. 07, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Noncontrolling interest	'	'	'	'
Noncontrolling interest	'	$10,788	'	'
Number of common stock exchangeable against each unit	'	1	'	'
Net income (loss) attributable to noncontrolling interest	'	1,359	'	'
Effects of changes in Athlon's partnership interest in Holdings on Athlon's equity	'	'	'	'
Net income attributable to stockholders	'	58,435	53,014	-1,129
Transfer from noncontrolling interest:	'	'	'	'
Shares of common stock in public offering	15,789,474	'	'	'
Athlon Holdings GP LLC	'	'	'	'
Noncontrolling interest	'	'	'	'
Ownership interest in general partner of Holdings (as a percent)	'	100.00%	'	'
Holdings	'	'	'	'
Noncontrolling interest	'	'	'	'
Percentage of ownership interest of management and certain employees (as a percent)	3.20%	2.20%	'	'
Effects of changes in Athlon's partnership interest in Holdings on Athlon's equity	'	'	'	'
Net income attributable to stockholders	'	59,063	'	'
Transfer from noncontrolling interest:	'	'	'	'
Increase in Athlon's paid-in capital for corporate reorganization	'	292,549	'	'
Increase in Athlon's paid-in capital for issuance of 15,789,474 shares of common stock in initial public offering	'	295,498	'	'
Shares of common stock in public offering	'	15,789,474	'	'
Net transfer from noncontrolling interest	'	588,047	'	'
Change from net income attributable to stockholders and transfers from noncontrolling interest	'	$647,110	'	'
Holdings \| Class A limited partners	'	'	'	'
Noncontrolling interest	'	'	'	'
Percentage of ownership interest of management and certain employees (as a percent)	3.20%	2.20%	'	'
Exchange Agreement Number of New Units Exchangeable Against Limited Partner Interest	1,855,563	'	'	'
Number of common stock exchangeable against each unit	'	1	'	'

Acquisitions_Details

Acquisitions (Details) (USD $)	0 Months Ended	12 Months Ended		0 Months Ended
	Oct. 03, 2011	Dec. 31, 2011	Oct. 03, 2011	Jan. 06, 2011	Jan. 06, 2011
	Element	Element	Element	SandRidge	SandRidge
			Apollo		Apollo
Acquisitions	'	'	'	'	'
Cash paid for acquisition	$253,200,000	'	'	$156,000,000	'
Transaction costs incurred	6,400,000	'	4,300,000	2,600,000	2,300,000
Allocation of the purchase price to the fair value of the assets acquired and liabilities assumed	'	'	'	'	'
Proved properties, including wells and related equipment	130,527,000	'	'	158,157,000	'
Unproved properties	123,107,000	'	'	'	'
Other assets	806,000	'	'	'	'
Oil inventory	'	'	'	637,000	'
Total assets acquired	254,440,000	'	'	158,794,000	'
Current liabilities	831,000	'	'	'	'
Asset retirement obligations	393,000	'	'	2,778,000	'
Total liabilities assumed	1,224,000	'	'	'	'
Fair value of net assets acquired	253,216,000	'	'	156,016,000	'
Unaudited pro forma condensed financial data	'	'	'	'	'
Pro forma total revenues	'	89,618,000	'	'	'
Pro forma net income attributable to stockholders	'	$9,777,000	'	'	'
Pro forma net income (loss) per common share:	'	'	'	'	'
Basic (in dollar per share)	'	$0.15	'	'	'
Diluted (in dollar per share)	'	$0.14	'	'	'

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (Level 1 input, USD $)	Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2013
Level 1 input	'
Fair value measurements	'
Senior notes	$522.80

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (USD $)

1 Months Ended

3 Months Ended

12 Months Ended

Oct. 31, 2011

Jan. 31, 2011

Sep. 30, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Mar. 31, 2014

Open commodity derivative contracts

Commodity derivative contracts with swap price

2014

2015

2014

2015

bbl

Summary of open commodity derivative contracts

Average Daily Swap Volume

7,950

1,300

Weighted-Average Swap Price

92.67

93.18

Asset (Liability) Fair Market Value

($6,024,000)

$3,989,000

($8,354,000)

$2,330,000

Net proceeds from monetization of put options

7,600,000

7,625,000

Interest expense

200,000

36,669,000

9,951,000

2,945,000

Initial payment of premiums

$2,000,000

Fair_Value_Measurements_Detail2

Fair Value Measurements (Details 3) (Master netting agreements, BNP Paribas, USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2013
Master netting agreements \| BNP Paribas	'
Counterparty risk	'
Fair Market Value of Oil Derivative Contracts Committed	$1,082

Fair_Value_Measurements_Detail3

Fair Value Measurements (Details 4) (Commodity contracts, USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Liabilities	'	'
Net assets (liabilities)	($6,024)	$3,989
Derivative instruments not designated as hedging instruments \| Oil	'	'
Assets	'	'
Oil Commodity Derivatives, assets	2,473	6,651
Commodity Derivatives Netting, assets	-143	-1,551
Total Commodity Derivatives	2,330	5,100
Liabilities	'	'
Oil Commodity Derivatives, liabilities	-8,497	-2,662
Commodity Derivatives Netting, liabilities	143	1,551
Total Commodity Derivatives	-8,354	-1,111
Net assets (liabilities)	-6,024	3,989
Derivative instruments not designated as hedging instruments \| Oil \| Derivative assets - current	'	'
Assets	'	'
Oil Commodity Derivatives, assets	143	3,386
Commodity Derivatives Netting, assets	-143	-1,140
Total Commodity Derivatives	'	2,246
Derivative instruments not designated as hedging instruments \| Oil \| Derivative assets - noncurrent	'	'
Assets	'	'
Oil Commodity Derivatives, assets	2,330	3,265
Commodity Derivatives Netting, assets	'	-411
Total Commodity Derivatives	2,330	2,854
Derivative instruments not designated as hedging instruments \| Oil \| Derivative liabilities - current	'	'
Liabilities	'	'
Oil Commodity Derivatives, liabilities	-8,497	-1,732
Commodity Derivatives Netting, liabilities	143	1,140
Total Commodity Derivatives	-8,354	-592
Derivative instruments not designated as hedging instruments \| Oil \| Derivative liabilities - noncurrent	'	'
Liabilities	'	'
Oil Commodity Derivatives, liabilities	'	-930
Commodity Derivatives Netting, liabilities	'	411
Total Commodity Derivatives	'	($519)

Fair_Value_Measurements_Detail4

Fair Value Measurements (Details 5) (Derivative instruments not designated as hedges, Commodity contracts, Derivative fair value loss (gain), USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative instruments not designated as hedges \| Commodity contracts \| Derivative fair value loss (gain)	'	'	'
Fair value measurements	'	'	'
Amount of Loss (Gain) Recognized in Income	$18,115	($9,293)	$7,959

Fair_Value_Measurements_Detail5

Fair Value Measurements (Details 6) (Commodity contracts, USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Fair Value Hierarchy	'	'
Increase (decrease) in net commodity derivative assets (liabilities)	($39,000)	$125,000
Recurring \| Net Asset (Liability) \| Oil	'	'
Fair Value Hierarchy	'	'
Total	'	3,989,000
Recurring \| Net Asset (Liability) \| Oil \| Swaps	'	'
Fair Value Hierarchy	'	'
Total	-6,024,000	4,069,000
Recurring \| Net Asset (Liability) \| Oil \| Collars	'	'
Fair Value Hierarchy	'	'
Total	'	-80,000
Recurring \| Significant Other Observable Inputs (Level 2) \| Oil	'	'
Fair Value Hierarchy	'	'
Total	'	3,989,000
Recurring \| Significant Other Observable Inputs (Level 2) \| Oil \| Swaps	'	'
Fair Value Hierarchy	'	'
Total	-6,024,000	4,069,000
Recurring \| Significant Other Observable Inputs (Level 2) \| Oil \| Collars	'	'
Fair Value Hierarchy	'	'
Total	'	($80,000)

Asset_Retirement_Obligations_D

Asset Retirement Obligations (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Asset retirement obligations	'	'	'
Balance at the beginning of the period	$5,049	$3,704	'
Liabilities assumed in acquisitions	395	60	'
Liabilities incurred from new wells	1,013	815	'
Liabilities settled	-283	'	'
Accretion of discount	675	478	344
Revisions of previous estimates	6	-8	'
Balance at the end of the period	6,855	5,049	3,704
Less: current portion	60	'	'
Asset retirement obligations - long-term	$6,795	$5,049	'

LongTerm_Debt_Details

Long-Term Debt (Details) (USD $)

12 Months Ended

1 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Apr. 30, 2013

Dec. 31, 2013

Nov. 30, 2013

31-May-13

Apr. 30, 2013

Dec. 31, 2013

Senior notes

Credit agreement

Former second lien term loan

Upon assets disposition triggering events

Prior to April 15, 2016

On or prior to July 15, 2014

Maximum

Applicable Margin for Eurodollar Loans

Applicable Margin for Base Rate Loans

Less than or equal to .30 to 1

Greater than .30 to 1 but less than or equal to .60 to 1

Greater than .60 to 1 but less than or equal to .80 to 1

Greater than .80 to 1 but less than or equal to .90 to 1

Greater than .90 to 1

Maximum

Minimum

Redemption from proceeds of certain equity offerings

Redemption of debt instrument upon change of control

Prior to April 15, 2016

Eurodollar rate

LIBOR

Eurodollar rate

LIBOR

Base Rate

Prime rate

Federal funds rate

Applicable Margin for Eurodollar Loans

Applicable Margin for Base Rate Loans

Applicable Margin for Eurodollar Loans

Applicable Margin for Base Rate Loans

Applicable Margin for Eurodollar Loans

Applicable Margin for Base Rate Loans

Applicable Margin for Eurodollar Loans

Applicable Margin for Base Rate Loans

Applicable Margin for Eurodollar Loans

Applicable Margin for Base Rate Loans

Less than or equal to .30 to 1

Greater than .30 to 1 but less than or equal to .60 to 1

Greater than .60 to 1 but less than or equal to .80 to 1

Greater than .80 to 1 but less than or equal to .90 to 1

Greater than .90 to 1

Greater than .30 to 1 but less than or equal to .60 to 1

Greater than .60 to 1 but less than or equal to .80 to 1

Greater than .80 to 1 but less than or equal to .90 to 1

Redemption from proceeds of certain equity offerings

Long-term debt

Aggregate principal amount of notes issued

$500,000,000

Interest rate (as a percent)

7.38%

Distribution paid to Holdings' Class A limited partners

75,000,000

Fixed charge coverage ratio

Percentage of aggregate principal amount of notes that can be redeemed

35.00%

Redemption price of debt instrument (as a percent)

101.00%

100.00%

107.38%

110.00%

Write off of unamortized debt issuance costs

2,800,000

Maximum amount committed by lender

1,000,000,000

Current borrowing base

525,000,000

320,000,000

267,500,000

Outstanding borrowings

Outstanding letters of credit

Ratio of Outstanding Borrowings to Borrowing Base

0.3

0.6

0.8

0.9

0.3

0.6

0.8

Unused Commitment Fee (as a percent)

0.38%

0.50%

Applicable Margin (as a percent)

1.00%

0.50%

1.50%

0.50%

1.75%

0.75%

2.00%

1.00%

2.25%

1.25%

2.50%

1.50%

Variable interest rate base

'Eurodollar rate

'LIBOR

'Eurodollar rate

'LIBOR

'Base Rate

'prime rate

'Federal fund

Ratio of consolidated total debt to EBITDAX beginning with quarter ended June 30, 2013

4.75

Ratio of consolidated total debt to EBITDAX beginning with quarter ended June 30, 2014

4.5

Maximum projected production that can be hedged (as a percent)

85.00%

Period over which hedging limitation requirement of the projected production from proved reserve is required to be maintained

'66 months

Long-Term Debt Maturities

Thereafter

500,000,000

Total

$500,000,000

Weighted-average interest rate (as a percent)

7.60%

4.30%

3.80%

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	0 Months Ended			12 Months Ended
Stockholders' Equity (Details) (USD $)	Aug. 07, 2013	Apr. 26, 2013	Apr. 02, 2013	Dec. 31, 2013
Stockholders' Equity	'	'	'	'
Common stock issued at incorporation (in shares)	'	'	1,000	'
Aggregate purchase price of common stock issued at incorporation (in dollars)	'	'	$10	'
Common stock issued in connection with corporate reorganization to certain holders of Class A and Class B limited partner interests in Holdings (in shares)	'	960,907	'	'
Issue price of IPO (in dollars per share)	$20	'	'	'
Stock split ratio	65.266	'	'	65.266
Outstanding common stock shares prior to closing of IPO	66,339,615	'	'	'
Shares of common stock issued in IPO	15,789,474	'	'	'
Net proceeds from IPO, after deducting underwriting discounts and commissions and offering expenses (in dollars)	$295,700,000	'	'	$295,697,000
Preferred Stock	'	'	'	'
Preferred stock, shares authorized	'	'	'	50,000,000
Preferred stock, shares issued	'	'	'	0
Preferred stock, shares outstanding	'	'	'	0
Holdings	'	'	'	'
Stockholders' Equity	'	'	'	'
Shares of common stock issued in IPO	'	'	'	15,789,474
Stockholders' equity	'	'	'	'
Percentage of ownership noncontrolling interest	3.20%	'	'	2.20%

Taxes_Details

Taxes (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Federal:	'	'	'
Current	$1,135	'	'
Deferred	17,022	'	'
Total federal	18,157	'	'
State, net of federal benefit:	'	'	'
Deferred	993	1,928	470
Total state	993	1,928	470
Income tax provision	19,150	1,928	470
Reconciliation of income tax benefit (provision) with income tax at the Federal statutory rate	'	'	'
Income (loss) before income taxes	79,572	54,942	-659
Less: net income prior to corporate reorganization	-27,320	'	'
Less: net income attributable to noncontrolling interest	-1,359	'	'
Income (loss) before income taxes and noncontrolling interest subsequent to corporate reorganization	50,893	54,942	-659
Income taxes at the Federal statutory rate	17,813	'	'
State income taxes, net of federal benefit	933	549	21
Provision to return adjustment	59	'	'
Permanent and other	345	1,379	449
Income tax provision	19,150	1,928	470
Assets:	'	'	'
Derivative fair value loss	480	'	'
Total current deferred tax assets	480	'	'
Liabilities:	'	'	'
Prepaid insurance	-100	-8	'
Derivative fair value gain	'	-50	'
Total current deferred tax liabilities	-100	-58	'
Net current deferred tax asset (liability)	380	'	'
Assets:	'	'	'
Alternative minimum tax credits	1,135	'	'
Derivative fair value loss	2,080	60	'
Net operating loss carryforward	43,164	'	'
Asset retirement obligations	519	8	'
Deferred equity-based compensation	1,406	'	'
Acquisition cost capitalized	3,351	95	'
Other	1,840	25	'
Total long-term deferred tax assets	53,495	188	'
Liabilities:	'	'	'
Book basis of oil and natural gas properties in excess of tax basis	-145,892	-2,528	'
Total long-term deferred tax liabilities	-145,892	-2,528	'
Net long-term deferred tax liability	-92,397	-2,340	'
Federal	'	'	'
Carryforwards and credits	'	'	'
Federal AMT Credits	1,135	'	'
Federal NOL	123,325	'	'
2031 \| Federal	'	'	'
Carryforwards and credits	'	'	'
Federal NOL	2,433	'	'
2032 \| Federal	'	'	'
Carryforwards and credits	'	'	'
Federal NOL	77,749	'	'
2033 \| Federal	'	'	'
Carryforwards and credits	'	'	'
Federal NOL	43,143	'	'
Indefinite \| Federal	'	'	'
Carryforwards and credits	'	'	'
Federal AMT Credits	$1,135	'	'

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	0 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Aug. 07, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 30, 2013
Earnings Per Share	'	'	'	'	'
Outstanding common stock prior to consummation of IPO (in shares)	'	'	'	'	960,907
Issue price of IPO (in dollars per share)	$20	'	'	'	'
Stock split ratio	65.266	65.266	'	'	'
Outstanding common stock shares prior to closing of IPO	66,339,615	'	'	'	'
Conversion of units into common stock	'	1	'	'	'
Numerator:	'	'	'	'	'
Undistributed net income (loss) attributable to stockholders	'	$59,063	$53,014	($1,129)	'
Participation rights of unvested RSUs in undistributed earnings	'	-628	'	'	'
Basic undistributed net income (loss) attributable to stockholders	'	58,435	53,014	-1,129	'
Denominator:	'	'	'	'	'
Basic weighted average shares outstanding	'	72,915,000	66,340,000	66,340,000	'
Basic EPS attributable to stockholders (in dollars per share)	'	$0.80	$0.80	($0.02)	'
Numerator:	'	'	'	'	'
Undistributed net income (loss) attributable to stockholders	'	59,063	53,014	-1,129	'
Participation rights of unvested RSUs in undistributed earnings, diluted	'	-613	'	'	'
Effect of conversion of New Holdings Units to shares of Athlon's common stock	'	1,359	'	'	'
Diluted undistributed net income (loss) attributable to stockholders	'	$59,809	$53,014	($1,129)	'
Denominator:	'	'	'	'	'
Basic weighted average shares outstanding	'	72,915,000	66,340,000	66,340,000	'
Effect of conversion of New Holdings Units to shares of Athlon's common stock	'	1,856,000	1,856,000	'	'
Diluted weighted average shares outstanding	'	74,771,000	68,196,000	66,340,000	'
Diluted EPS attributable to stockholders (in dollars per share)	'	$0.80	$0.78	($0.02)	'
Antidilutive New Holdings Units excluded from EPS calculations (in shares)	'	'	'	1,855,563	'

Employment_Benefit_Plans_Detai

Employment Benefit Plans (Details) (USD $)	0 Months Ended	12 Months Ended
Employment Benefit Plans (Details) (USD $)	Aug. 07, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
401(k) Plan	'	'	'	'
Employers contributions	'	$585,000	$454,000	$219,000
Incentive award plan	'	'	'	'
Non-cash equity-based compensation expense	'	5,307,000	152,000	106,000
2013 Incentive Award Plan	'	'	'	'
Incentive award plan	'	'	'	'
Aggregate shares of common stock available for issuance under the 2013 stock incentive plan	'	8,400,000	'	'
Remaining shares available for grant	'	7,761,087	'	'
Non-cash equity-based compensation expense	'	4,000,000	'	'
Capitalized non-cash equity-based compensation expense	'	263,000	'	'
2013 Incentive Award Plan \| RSUs	'	'	'	'
Incentive award plan	'	'	'	'
Vesting period of RSU's	'	'3 years	'	'
Unvested RSUs	'	'	'	'
Granted (in shares)	'	638,913	'	'
Weighted - Average Grant Date Fair Value	'	'	'	'
Granted (in dollars per share)	'	$34.88	'	'
Outstanding at end of the period (in dollars per share)	'	$34.88	'	'
Additional disclosure	'	'	'	'
Unvested RSUs subject to variable accounting (in shares)	'	0	'	'
Total unrecognized compensation cost related to unvested RSU's	'	16,600,000	'	'
Weighted-average period for recognition of unrecognized compensation cost	'	'2 years 7 months 6 days	'	'
2013 Incentive Award Plan \| RSUs \| Vesting of awards subject to time and continued employment condition	'	'	'	'
Unvested RSUs	'	'	'	'
Outstanding at end of the period (in shares)	'	411,413	'	'
Additional disclosure	'	'	'	'
Unvested RSUs granted, vesting of which is dependent on passage of specified time and continued employment condition (in shares)	'	411,413	'	'
Vesting of awards in 2014 (in shares)	'	137,138	'	'
Vesting of awards in 2015 (in shares)	'	137,138	'	'
Vesting of awards in 2016 (in shares)	'	137,137	'	'
Outstanding RSUs	'	411,413	'	'
2013 Incentive Award Plan \| RSUs \| Vesting of awards subject to time, continued employment and performance condition	'	'	'	'
Unvested RSUs	'	'	'	'
Outstanding at end of the period (in shares)	'	227,500	'	'
Additional disclosure	'	'	'	'
Unvested RSUs granted, vesting of which is dependent on passage of specified time and continued employment and also on performance condition (in shares)	'	227,500	'	'
Vesting of awards in 2014 (in shares)	'	75,834	'	'
Vesting of awards in 2015 (in shares)	'	75,833	'	'
Vesting of awards in 2016 (in shares)	'	75,833	'	'
Outstanding RSUs	'	227,500	'	'
Percentage of maximum number of shares that could be earned under the performance-based awards	'	50.00%	'	'
Percentage of designated target vesting levels under the performance-based awards	'	100.00%	'	'
Maximum \| 2013 Incentive Award Plan	'	'	'	'
Incentive award plan	'	'	'	'
Aggregate shares of common stock available for issuance under the 2013 stock incentive plan at January 1, 2014 under first condition	'	12,000,000	'	'
Percentage increase to shares of common stock available for issuance under the 2013 stock incentive plan at January 1, 2014 under second condition	'	4.00%	'	'
Maximum \| 2013 Incentive Award Plan \| Non-employee directors	'	'	'	'
Incentive award plan	'	'	'	'
Grant date fair value of awards	'	700,000	'	'
Holdings \| Class B limited partners	'	'	'	'
Incentive award plan	'	'	'	'
Non-cash equity-based compensation expense	1,500,000	1,300,000	152,000	106,000
Capitalized non-cash equity-based compensation expense	'	$415,000	$93,000	'

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended
Commitments and Contingencies (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating leases, payments due by period	'	'	'
Total	$1,316,000	'	'
2014	467,000	'	'
2015	471,000	'	'
2016	378,000	'	'
Operating lease rental expense	490,000	507,000	272,000
Minimum	'	'	'
Leases	'	'	'
Non-cancelable lease terms	'1 year	'	'
Corporate office lease	'	'	'
Operating leases, payments due by period	'	'	'
Total	1,031,000	'	'
2014	375,000	'	'
2015	375,000	'	'
2016	281,000	'	'
Midland office lease	'	'	'
Operating leases, payments due by period	'	'	'
Total	285,000	'	'
2014	92,000	'	'
2015	96,000	'	'
2016	$97,000	'	'

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)	12 Months Ended			35 Months Ended
Related Party Transactions (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Aug. 07, 2013
Related party transactions	'	'	'	'
Termination fee	$2,408,000	'	'	'
Distribution paid to Holdings' Class A limited partners	75,000,000	'	'	'
Number of common stock exchangeable against each unit	1	'	'	'
Percentage of income tax benefits distributable to holders of New Holdings Units	85.00%	'	'	'
Apollo	'	'	'	'
Related party transactions	'	'	'	'
Transaction fee as a percentage of total equity contributed	2.00%	'	'	'
Transaction fees	'	'	'	7,500,000
Consulting and advisory fee as percentage of EBITDAX under first condition	1.00%	'	'	'
Advisory fee per quarter under second condition	62,500	'	'	'
Maximum advisory fee per calendar year	500,000	'	'	'
Advisory fee	500,000	493,000	411,000	'
Termination fee	2,400,000	'	'	'
Unreimbursed fee on termination of the service agreement	132,000	'	'	'
Apollo Global Securities, LLC	'	'	'	'
Related party transactions	'	'	'	'
Proceeds from gross spread	500,000	'	'	'
Payment of discounts and commissions to underwriters in IPO	900,000	'	'	'
Apollo funds	'	'	'	'
Related party transactions	'	'	'	'
Distribution paid to Holdings' Class A limited partners	73,000,000	'	'	'
Management team and certain employees	'	'	'	'
Related party transactions	'	'	'	'
Distribution paid to Holdings' Class A limited partners	$2,000,000	'	'	'
Number of common stock exchangeable against each unit	1	'	'	'

Subsequent_Events_Details

Subsequent Events (Details) (USD $)

Mar. 31, 2014

Feb. 06, 2014

Mar. 07, 2014

In Millions, unless otherwise specified

Commodity derivative contracts with swap price

Subsequent event

2014

2015

Midland Basin

Commodity derivative contracts with swap price

bbl

Q1 2014

Q2 2014

Q3 2014

Q4 2014

Q1 2015

Q2 2015

Q3 2015

Q4 2015

2014

2015

Oil

bbl

Subsequent events

Average Daily Swap Volume

7,950

1,300

8,606

8,950

9,950

4,300

1,300

9,369

2,788

Weighted-Average Swap Price

92.67

93.18

92.7

92.71

92.52

91.29

93.18

92.61

91.74

Cash paid for acquisition

$88

Increase in purchase price

$8.70