Significant Commitments by Category (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Minimum Rental Commitments
2013	$ 2,093
2014	1,810
2015	1,613
2016	1,481
2017	653
Thereafter	1,347
Total	8,997
Drilling Commitments
Commitments
2013	22,117
2014	0
2015	0
2016	0
2017	0
Thereafter	0
Total	22,117
Firm Transportation Commitments
Commitments
2013	4,580
2014	2,002
2015	2,002
2016	1,095
2017	1,095
Thereafter	11,862
Total	$ 22,636

Contractual Commitments Future Minimum Payments Due

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Contractual Commitments Future Minimum Payments Due In Four Years

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Contractual Commitments Future Minimum Payments Due In Three Years

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Contractual Commitments Future Minimum Payments Due In Two Years

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Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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