Equity in Net Assets of Investee Companies - Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Sales	$ 317,183	$ 232,145	$ 274,183
Gross profit	53,161	23,739	42,143
Net income	23,954	3,072	15,254
Company's dividends received	2,826	4,307	$ 1,887
Equity Method Investment, Summarized Financial Information, Balance Sheet [Abstract]
Current assets	162,893	139,146
Property, plant and equipment and other assets	53,941	54,674
Current liabilities	103,687	102,550
Long-term obligations and other liabilities	$ 5,067	$ 7,432