Long-Term Debt - Additional Information (Detail) (USD $)	0 Months Ended	12 Months Ended			3 Months Ended	6 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended		12 Months Ended					12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013 10.375% Senior Unsecured Notes due 2016	Jun. 30, 2013 10.375% Senior Unsecured Notes due 2016	Dec. 31, 2013 10.375% Senior Unsecured Notes due 2016	Jun. 30, 2013 Senior Notes Due 2020 [Member]	Dec. 31, 2013 Revolving credit facility	Sep. 30, 2012 Revolving credit facility	Dec. 31, 2013 Revolving credit facility Minimum	Dec. 31, 2013 Revolving credit facility Maximum	Dec. 31, 2013 Revolving credit facility through December 31, 2013 Maximum	Dec. 31, 2013 Revolving credit facility through June 30, 2014 Maximum	Dec. 31, 2013 Revolving credit facility through maturity Maximum	Dec. 31, 2013 Revolving credit facility Group Twelve	Dec. 31, 2013 Revolving credit facility Group Thirteen	Sep. 30, 2012 Revolving credit facility Letter of Credit	Dec. 31, 2013 Previous Revolving Credit Facility	Sep. 30, 2012 Previous Revolving Credit Facility	Dec. 31, 2009 10.375% Senior Unsecured Notes due 2016	Dec. 31, 2013 7.25% Senior Unsecured Notes due 2019	Feb. 29, 2012 7.25% Senior Unsecured Notes due 2019	Dec. 31, 2013 7.25% Senior Unsecured Notes due 2019 Group One	Dec. 31, 2013 7.25% Senior Unsecured Notes due 2019 Group Two
Debt Disclosure [Line Items]
Maximum borrowing capacity										$ 400,000,000								$ 20,000,000
Optional additional borrowing									200,000,000
Debt Instrument Initial Borrowing Capacity Amount																				425,000,000
Letter of credit amount outstanding																			2,700,000
Available borrowing capacity																			191,300,000
Debt issuance costs paid		25,634,000	2,032,000	8,854,000
Write off of deferred debt issuance cost						10,000,000
Credit facility interest rate description									Borrowings under the Revolver bear interest, at our option, at either (i) a rate derived from the London Interbank Offered Rate, as adjusted for statutory reserve requirements for Eurocurrency liabilities (the “Adjusted LIBOR”), plus an applicable margin ranging from 1.500% to 2.500% or (ii) the greater of (a) the prime rate, (b) the federal funds effective rate plus 0.5% or (c) the one-month Adjusted LIBOR plus 1.0%, and, in each case, plus an applicable margin (ranging from 0.500% to 1.500%). The applicable margin is determined based on the ratio of our outstanding borrowings to the available Revolver capacity.
Credit facility interest rate option one, applicable margin rate over Adjusted LIBOR											1.50%	2.50%
Credit facility interest rate option two, base rate over federal funds effective rate									0.50%
Debt Instrument, Description of Variable Rate Basis		one-month Adjusted LIBOR
Credit facility interest rate option two, base rate over one-month Adjusted LIBOR									1.00%
Credit facility interest rate option two, applicable margin rate									2.00%		0.50%	1.50%
Line of Credit Facility, Interest Rate at Period End									2.1875%
Line Of Credit Facility, Interest Rate at Period End, LIBOR Component									0.1875%
Commitment fees for undrawn credit facility	0.50%															0.375%	0.50%
Current ratio											1.0
Debt to EBITDAX ratio													4.5	4.25	4.0
Annual interest rate																					10.375%	7.25%	7.25%
Redemption option, percent of principal																								103.625%	100.00%
Cash paid to repurchase principal					330,900,000
Loss On extinguishment of debt ross							(29,200,000)
Loss on extinguishment of debt		29,174,000	3,164,000	25,421,000
Debt Proceeds Used For Cash Consideration, Business Acquisition								$ 380,000,000