Long-Term Debt (Narrative) (Details) (USD $)	12 Months Ended													9 Months Ended													0 Months Ended												0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Dec. 31, 2013 Senior Notes [Member]		Sep. 30, 2013 Senior Notes [Member]	Dec. 31, 2012 Senior Notes [Member]		Dec. 21, 2012 Senior Notes [Member]	Oct. 17, 2012 Senior Notes [Member]		Oct. 09, 2012 Senior Notes [Member]	Sep. 30, 2013 Building Loans [Member]	Dec. 31, 2013 Building Loans [Member]		Dec. 31, 2012 Building Loans [Member]		Mar. 31, 2011 Building Loans [Member]	Oct. 09, 2012 Minimum [Member] Senior Notes [Member]	Oct. 09, 2012 Maximum [Member] Senior Notes [Member]	Dec. 24, 2010 Amegy Bank National Association [Member]	Sep. 30, 2010 Amegy Bank National Association [Member]	Oct. 31, 2011 Nova Scotia, KeyBank, Societe Generale [Member]	May 03, 2011 Nova Scotia, KeyBank, Societe Generale [Member]	May 02, 2012 Credit Suisse, Deutche Bank, IberiaBank,KeyBank,Amegy Bank, Nova Scotia [Member]	Dec. 18, 2012 Nova Scotia, Amegy, KeyBank [Member]	Oct. 19, 2012 Nova Scotia, Amegy, KeyBank [Member]	Oct. 17, 2012 Nova Scotia, Amegy, KeyBank [Member]	Dec. 31, 2013 Nova Scotia, Amegy, KeyBank [Member]	Dec. 27, 2013 Nova Scotia, Amegy, KeyBank [Member]	Jun. 06, 2013 Nova Scotia, Amegy, KeyBank [Member]	May 03, 2011 Nova Scotia, Amegy, KeyBank [Member]	Sep. 30, 2010 Nova Scotia, Amegy, KeyBank [Member]	Dec. 31, 2013 Nova Scotia, Amegy, KeyBank [Member] Letter of Credit [Member]	Dec. 18, 2012 Nova Scotia, Amegy, KeyBank [Member] Senior Notes [Member]	Oct. 17, 2012 Nova Scotia, Amegy, KeyBank [Member] Senior Notes [Member]	Oct. 09, 2012 Nova Scotia, Amegy, KeyBank [Member] Senior Notes [Member]	Jun. 06, 2013 Base Rate Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Dec. 18, 2012 Base Rate Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Oct. 19, 2012 Base Rate Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Oct. 17, 2012 Base Rate Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Jun. 06, 2013 Euro Dollar Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Dec. 18, 2012 Euro Dollar Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Oct. 19, 2012 Euro Dollar Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Oct. 17, 2012 Euro Dollar Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Dec. 18, 2012 Federal Funds Rate [Member] Base Rate Loans [Member] Nova Scotia, Amegy, KeyBank [Member]	Dec. 18, 2012 Eurodollar [Member] Base Rate Loans [Member] Nova Scotia, Amegy, KeyBank [Member]
Debt Instrument [Line Items]
Interest cost capitalized, undeveloped properties	$ 7,132,000
Interest capitalized	7,132,000	0	0
Revolving credit facility																							100,000,000		350,000,000.0				45,000,000.0		1,500,000,000.0		350,000,000.0
Interest expense	17,490,000	7,458,000	1,400,000																								100,000															1,100,000
Borrowing capacity																						65,000,000.0	50,000,000.0	125,000,000.0	90,000,000.0	155,000,000.0	40,000,000.0		45,000,000.0	143,600,000.0	150,000,000.0	50,000,000.0		50,000,000.0
Senior unsecured notes issued																																				50,000,000.0	250,000,000.0	300,000,000
Applicable rate, minimum																																							0.50%	0.50%	0.75%	1.00%	1.50%	1.50%	1.75%	2.00%
Applicable rate, maximum																																							1.50%	1.50%	1.50%	1.75%	2.50%	2.50%	2.50%	2.75%
Commitment fee percentage																												0.375%	0.50%
Stated interest rate							7.75%				7.75%								5.82%																	7.75%	7.75%
Credit facility outstanding																														0					6,400,000.0
Basis spread																																															0.50%	1.00%
Debt instrument, description of rate																											LIBOR01
Debt covenant ratio for reasonable transactions				2.00
Debt covenant ratio for EBITDAX				3.00
Building Loan Outstanding Amount Of Building Loan Refinanced	301,995,000				300,000,000	[1]		300,000,000	[1]		300,000,000	[1]			1,995,000	[2]	2,143,000	[2]	2,400,000
Loan, periodic payment														22,000
Debt issued										50,000,000.0	250,000,000.0
Redemption of principal amount plus aggregate net proceeds													100.00%								35.00%
Percentage of notes required to be outstanding for redemption																				65.00%
Discount issue price, price											98.534%
Premium issue price, percent										101.00%
Unamortized discount	3,200,000										3,700,000
Effective interest rate										7.531%	8.00%
Unamortized premium	$ 400,000									$ 500,000

[1] On October 17, 2012, the Company issued $250.0 million in aggregate principal amount of October Notes to qualified institutional buyers pursuant to Rule 144A under the Securities Act and to certain non-U.S. persons in accordance with Regulation S under the Securities Act, (the "October Notes Offering") under an indenture among the Company, its subsidiary guarantors and Wells Fargo Bank, National Association, as the trustee, (the "senior note indenture"). On December 21, 2012, the Company issued an additional $50.0 million in aggregate principal amount of December Notes to qualified institutional buyers pursuant to Rule 144A under the Securities Act and to certain non-U.S. persons in accordance with Regulation S under the Securities Act ("the December Notes Offering"). The December Notes were issued as additional securities under the senior note indenture. The October Notes Offering and the December Notes Offering are collectively referred to as the "Notes Offerings". The Company used a portion of the net proceeds from the October Notes Offering to repay all amounts outstanding at such time under its revolving credit facility. The Company used the remaining net proceeds of October Notes Offering and the net proceeds of the December Notes Offering for general corporate purposes, which included funding a portion of its 2013 capital development plan. Under the senior note indenture, interest on the Notes accrues at a rate of 7.75% per annum on the outstanding principal amount from October 17, 2012, payable semi-annually on May 1 and November 1 of each year, commencing on May 1, 2013. The Notes are the Company's senior unsecured obligations and rank equally in the right of payment with all of the Company's other senior indebtedness and senior in right of payment to any future subordinated indebtedness. All of the Company's existing and future restricted subsidiaries that guarantee the Company's secured revolving credit facility or certain other debt guarantee the Notes; provided, however, that the Notes are not guaranteed by Grizzly Holdings, Inc. and will not be guaranteed by any of the Company's future unrestricted subsidiaries. The Company may redeem some or all of the Notes at any time on or after November 1, 2016, at the redemption prices listed in the senior note indenture. Prior to November 1, 2016, the Company may redeem the Notes at a price equal to 100% of the principal amount plus a “make-whole” premium. In addition, prior to November 1, 2015, the Company may redeem up to 35% of the aggregate principal amount of the Notes with the net proceeds of certain equity offerings, provided that at least 65% of the aggregate principal amount of the Notes initially issued remains outstanding immediately after such redemption.

[2] In March 2011, the Company entered into a new building loan agreement for the office building it occupies in Oklahoma City, Oklahoma. The new loan agreement refinanced the $2.4 million outstanding under the previous building loan agreement. The new agreement matures in February 2016 and bears interest at the rate of 5.82% per annum. The new building loan requires monthly interest and principal payments of approximately $22,000 and is collateralized by the Oklahoma City office building and associated land.