Equity Method Investments and Related-Party Transactions - The Difference Between Carrying Value of Investment in Euro Infrastructure Co. and Proportionate Share of Net Assets of Euro Infrastructure Co. (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Mar. 31, 2020
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated affiliate	$ 162,168	$ 160,204
Euro Infrastructure Co [Member]
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated affiliate	162,168	160,204
Less: proportionate share of net assets of Euro Infrastructure Co.	146,428	144,769
Excess carrying value of investment over proportionate share of net assets	15,740	15,435
Euro Infrastructure Co [Member] | Goodwill [Member]
Schedule of Equity Method Investments [Line Items]
Excess carrying value of investment over proportionate share of net assets	22,042	21,777
Euro Infrastructure Co [Member] | Identifiable Intangible Assets [Member]
Schedule of Equity Method Investments [Line Items]
Excess carrying value of investment over proportionate share of net assets	8,125	8,799
Euro Infrastructure Co [Member] | Tangible Assets [Member]
Schedule of Equity Method Investments [Line Items]
Excess carrying value of investment over proportionate share of net assets	(15,422)	(16,142)
Euro Infrastructure Co [Member] | Deferred Income Taxes [Member]
Schedule of Equity Method Investments [Line Items]
Excess carrying value of investment over proportionate share of net assets	$ 995	$ 1,001