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Investments In Unconsolidated Entities - Additional Information (Detail) - USD ($) | 3 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Mar. 31, 2017 | Jun. 30, 2020 | Dec. 31, 2012 | Dec. 31, 2019
Schedule of Equity Method Investments [Line Items] |  |  |  |
Investment carrying value |  | $ 1,500,000 |  | $ 1,500,000
Greg Stemm [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Investment carrying value |  | $ 1,500,000 |  | $ 1,500,000
Chatham Rock Phosphate, Ltd. [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Investment carrying value |  |  | $ 0 |
Deep sea mining exploratory services |  |  | $ 1,680,000 |
Shares received from CRP | 141,884 |  | 9,320,348 |
Outstanding equity stake in CRP | 1.00% |  |  |
Neptune Minerals, Inc. [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership percentage |  | 14.00% |  |
Investment carrying value |  | $ 0 |  |
Neptune Minerals, Inc. [Member] | Common Class B Non Voting Shares [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Current investment position in NMI |  | 3,092,488 |  |
Aggregate number of shares converted |  | 261,200 |  |
Neptune Minerals, Inc. [Member] | Series A Preferred Non Voting Shares [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Current investment position in NMI |  | 2,612 |  |
Dorado Ocean Resources, Ltd. [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Loss from unconsolidated entity |  | $ 21,300,000 |  |

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