Investments, at Equity, and Advances to 50% or Less Owned Companies - Schedule of Equity Investments (Parenthetical) (Details)	Mar. 31, 2021
OSV Partners
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage	30.40%	[1]
General Partner
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage	66.70%
Limited Partner | OSV Partners
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage	29.70%

[1] The Company owns 66.7% of the General Partner and 29.7% of the limited partnership interest of OSV Partners.