Deferred Income - Additional Information (Detail) - USD ($)	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	$ 5,191,654	$ 4,432,056	$ 4,362,056
Time and Bareboat Deferred Revenue [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	$ 5,191,654		$ 4,366,091

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Period Type:	instant