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Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 1 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended |  | 1 Months Ended | 3 Months Ended | 48 Months Ended | 1 Months Ended | 12 Months Ended
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Jul. 31, 2012 | Dec. 31, 2010 | Dec. 31, 2013 Well | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2013 Ovaka Well | Dec. 31, 2013 Gabon Obligation | Dec. 31, 2012 Gabon Obligation | Dec. 31, 2011 Gabon Obligation | Dec. 31, 2013 Offshore Gabon Sqkms | Mar. 31, 2014 Offshore Gabon Subsequent Events | Dec. 31, 2013 Offshore Gabon Seismic Obligation Sqkms Well | Dec. 31, 2013 Offshore Gabon Omangou Prospect Well | Nov. 30, 2006 Angola Well | Dec. 31, 2013 Angola acre Well | Dec. 31, 2012 Angola | Jan. 31, 2007 Angola Seismic Obligation Sqkms | Dec. 31, 2008 Angola Seismic Obligation Sqkms | Nov. 01, 2010 Angola Seismic Obligation Sqkms | Sep. 30, 2012 South Dakota acre | Dec. 31, 2013 South Dakota
Commitments And Contingencies Textual Abstract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of Charter |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Company s share of the charter payment |  |  |  | 28.10% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Charter fee for production up to 20,000 BOPD |  |  | 0.93 |  | 0.25 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Charter fee for those bbls produced in excess of 20,000 BOPD |  |  | 2.50 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Company's share of charter expense |  |  | $ 10.4 | $ 9.7 | $ 7.3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rent expense, operating leases |  |  | 4.1 | 4.4 | 3.6 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Extended drilling period | 2 years | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities, guarantees' fair value |  |  | 1.1 | 1.2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Discount |  |  |  |  |  |  | 25.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contractual Obligation Company Share |  |  |  |  |  |  | 3.0 | 3.7 | 2.8 |  |  |  |  |  |  |  |  |  |  |  |
Contractual Obligation accrued amount |  |  |  |  |  |  | 2.9 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost for acquire property |  |  |  |  |  |  |  |  |  | 5.3 |  |  |  |  |  |  |  |  |  |  |
Length of acquired property |  |  |  |  |  |  |  |  |  | 150 |  |  |  |  |  |  |  |  |  |  |
Number of exploration wells |  |  |  |  |  |  |  |  |  |  |  | 2 | 1 | 2 |  |  |  |  |  |  |
Cost related to drilling |  |  |  |  |  | 17.2 |  |  |  |  |  |  | 8.6 | 29.5 |  |  |  |  |  |  |
Cost related to share of drilling |  |  |  |  |  | 5.9 |  |  |  |  |  |  | 2.6 |  |  |  |  |  |  |  |
Cost related to drilling |  |  |  |  |  | 17.2 |  |  |  |  |  |  | 8.6 | 29.5 |  |  |  |  |  |  |
Cost related to share of drilling |  |  |  |  |  | 5.9 |  |  |  |  |  |  | 2.6 |  |  |  |  |  |  |  |
Acquisition related to obligation |  |  |  |  |  |  |  |  |  |  |  | 223 |  |  |  |  |  |  |  |  |
Number of exploration wells drilling required to pay remaining obligation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual funding related to production license, term |  |  |  |  |  |  |  |  |  |  | 7 years |  |  |  |  |  |  |  |  |  |
Percentage of annual funding over seven years |  |  |  |  |  |  |  |  |  |  | 12.14% |  |  |  |  |  |  |  |  |  |
Percentage of annual funding over last three years |  |  |  |  |  |  |  |  |  |  | 5.00% |  |  |  |  |  |  |  |  |  |
Abandonment cost related to annual funding |  |  | 10.1 |  |  |  |  |  |  | 10.1 |  |  |  |  |  |  |  |  |  |  |
Length of acquired property |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,175 | 524 | 1,000 |  |
Area under acquire property exploration rights agreement term |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,400,000 |  |  |  |  |  |
Joint operation agreement related to third party in working interest percentage |  |  |  |  |  |  |  |  |  |  |  |  |  | 40.00% |  |  |  |  |  |  |
Additional joint operation agreement related to third party in working interest percentage |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |  |  |  |
Production license agreement term |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |  |  |  |
Production license agreement term extended by government |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |
Drilling cost to company |  |  |  |  |  |  |  |  |  |  |  |  |  | 14.8 |  |  |  |  |  |  |
Seismic obligation cost to company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.75 | 3.00 |  |  |
Cost related to seismic obligation, gross |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7.5 | 6.0 |  |  |
Percentage of working interest for amounts owned |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40.00% |  |  |  |  | 100.00% |
Percentage of carried interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |  |  |
Allowance for accounts with partners |  |  | 7.6 | 6.0 |  |  |  |  |  |  |  |  |  |  |  | 7.6 |  |  |  |  |
Allowance recorded for accounts receivable with remainder |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.6 |  |  |  |  |  |
Gross area of acquired property |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10,000 |
Additional amount to drill and complete additional well |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.6
Dry hole Costs (Drilling Expenses) |  |  | 23.9 | 37.3 | 0.1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.9
Percentage of working interest for amounts owned |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40.00% |  |  |  |  | 100.00% |
Well penalty, minimum |  |  | 5.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Well penalty, maximum |  |  | 10.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Recorded restricted cash |  |  | $ 10.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of exploration wells intended for drilling after working interest assignment completed |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |

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