Related Party Transactions - Marine (Details) - Marine Products - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 31, 2015
Related party transactions:
Ownership percentage	100.00%			50.00%
Transition Support Services Agreement [Member]
Related party transactions:
Related party charges	$ 846,000	$ 865,000	$ 873,000
Due from related party, current	$ 49,000	$ 55,000

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

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Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date within one year where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth.

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