Cumulative and outstanding losses.

No definition available.

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- Definition

Equity method investments number of shares owned.

+ References

No definition available.

+ Details

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- Definition

Equity method investments shares owned.

+ References

No definition available.

+ Details

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- Definition

Mining exploratory service revenue.

+ References

No definition available.

+ Details

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- Definition

Shares received from unconsolidated entities.

+ References

No definition available.

+ Details

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- Definition

The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

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- Definition

Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company after stock transaction.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Investments in Unconsolidated Entities - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2012
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		142,100	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 A [Member]
Schedule of Equity Method Investments [Line Items]
Shares owned	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