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	Jun. 30, 2018	Mar. 31, 2018
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated affiliate	$ 169,454	$ 163,835
Euro Infrastructure Co [Member]
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated affiliate	169,454	163,835
Less: proportionate share of net assets of Euro Infrastructure Co.	152,200	147,115
Excess carrying value of investment over proportionate share of net assets	17,254	16,720
Euro Infrastructure Co [Member] | Goodwill [Member]
Schedule of Equity Method Investments [Line Items]
Excess carrying value of investment over proportionate share of net assets	24,188	23,523
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	12,773	12,839
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	(21,441)	(21,342)
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	$ 1,734	$ 1,700