Long-Term Debt - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended					12 Months Ended			12 Months Ended		12 Months Ended			0 Months Ended				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Letter of Credit[Member]	Feb. 25, 2014 Letter of Credit[Member] Subsequent Event [Member]	Dec. 31, 2013 Bank debt [Member]	Dec. 31, 2012 Bank debt [Member]	Apr. 26, 2011 Bank debt [Member]	Dec. 31, 2013 Bank Credit Facility[Member]	Feb. 25, 2014 Bank Credit Facility[Member] Subsequent Event [Member]	Dec. 31, 2013 1.75% Senior Convertible Notes due 2017 [Member]	Dec. 31, 2012 1.75% Senior Convertible Notes due 2017 [Member]	Mar. 06, 2012 1.75% Senior Convertible Notes due 2017 [Member]	Nov. 27, 2013 7.5% Senior Notes due 2022 [Member]	Nov. 08, 2012 7.5% Senior Notes due 2022 [Member]	Dec. 31, 2013 7.5% Senior Notes due 2022 [Member]	Dec. 31, 2012 7.5% Senior Notes due 2022 [Member]	Dec. 31, 2013 8.625% Senior Notes due 2017 [Member]	Dec. 31, 2012 8.625% Senior Notes due 2017 [Member]	Nov. 17, 2010 8.625% Senior Notes due 2017 [Member]	Jan. 26, 2010 8.625% Senior Notes due 2017 [Member]
Debt Instrument [Line Items]
Credit facility initial date							Apr. 26, 2011
Redetermined base borrowing and credit facility									$ 700,000
Maturity of new credit facility if note issue under 2004 indenture are retired on or before April 15, 2014										Apr. 26, 2015
Initial bank and availability under facility							400,000			378,594	378,594
Outstanding borrowing under bank credit facility					21,406	21,406				0	0
Period in which outstanding amount has to be repaid to cure deficiency							10 days
Period in which bank has to add new properties to borrowing base and has to grant mortgage to banks							30 days
Oil and gas reserve as proportion of discounted present value of future net cash flow, for mortgage							80.00%
Debt to EBITDA ratio, as defined in credit agreement							not greater than 3.25 for preceding four quarter
EBITDA to consolidated net interest, as defined in credit agreement							not less than 3.0 for preceding four quarter
Debt to EBITDA ratio							1.73 to 1
EBITDA to consolidated net interest ratio							18.40 to 1
Aggregate principal amount of senior notes													300,000	300,000	475,000	300,000					100,000	275,000
Initial conversion rate of convertible note 2017												An initial conversion rate of 23.4449 shares of our common stock per $1 principal amount of 2017 Convertible Notes
Initial conversion rate of common stock												23.4449
Principal amount of 2017 convertible notes												$ 1
Initial conversion price of convertible note 2017												$ 42.65
Closing share price												$ 34.59
Convertible notes principal amount												1
Percentage of current conversion price lower than closing sale price												130.00%
Maximum trading day												20 days
Consecutive trading days ending on last trading day												30 days
Period in which distribution is made to all holders of common stock rights, option or warrants												45 days
Consecutive trading days immediately preceding, but excluding, declaration date												10 days
Percentage in which distribution has per share value exceeding closing sale price of common stock												10.00%
Percentage in which closing sale price of common stock is excess of convertible notes												98.00%
Number of consecutive business day												5 days
Number of consecutive trading day												25 days
Payment for call option												70,830
Anti-dilution adjustments for purchases of call option												7,033,470
Strike price per share												$ 55.91
Proceeds from sale of warrants												40,170
Liability component of convertible note	1,027,084	1,027,084	914,126									252,084	239,126				775,000	300,000		375,000
Accrued interest payment												1,750
Interest cost related to amortization of discount												12,959	9,956
Amortization of deferred financing cost												1,238	951
Interest expense related to contractual interest coupon of convertible notes												5,250	4,302
Proceeds from issuance of senior notes		489,250	300,000												480,195	293,203
Effective interest rates	7.51%	7.51%	7.75%	7.04%											3.00%
Redemption of senior notes																35.00%
Equity offerings redemption price																107.50%
Accrued interest payment	9,022	9,022	18,546														7,266
Total cost of the redemption																			406,967
Cost of redemption excluding accrued and unpaid interest																			396,014
Accrued and unpaid interest																			10,953
Redemption resulted in a charge to earnings	(27,279)	(27,279)	(1,972)	(607)															27,279
Premium paid for the repurchase and redemption																			21,014
Deferred financing costs write off																			6,265
Deferred financing costs, net of accumulated amortization	11,754	11,754	27,753
Total interest cost incurred		$ 79,697	$ 68,031	$ 51,322