Share Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	$ 15,425	$ 13,399	$ 8,914
Stock based compensation capitalized into oil and gas properties	5,078	4,288	3,010
Exercise price of stock options outstanding, minimum	$ 6.97
Exercise price of stock options outstanding, maximum	$ 53.20
Restricted stocks issued, shares	848,498	670,818	597,062
Restricted stocks issued, value	17,487,000	21,085,000	14,100,000
Unrecognized compensation cost, weighted average period of recognition	1 year 8 months 12 days
Unrecognized compensation cost	17,004,000
Adjustments to additional paid-in capital related to net tax effect of stock options exercises and restricted stock vesting	(884,000)	814,000	735,000
Restricted Stock[Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	15,405	13,308	8,796
Restricted Stock[Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock options	1 year
Restricted Stock[Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock options	3 years
Stock Options[Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	$ 20	$ 91	$ 118
2009 plan [Member] | All Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock options	5 years
Period after which stock option will expire subsequent to award	10 years
2009 plan [Member] | Non - Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock options	3 years
Period after which stock option will expire subsequent to award	10 years