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, 2017	Mar. 31, 2017
Schedule of Equity Method Investments [Line Items]
Carrying value of investment in Euro Infrastructure Co.	$ 144,289	$ 141,894
Euro Infrastructure Co [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value of investment in Euro Infrastructure Co.	144,289	141,894
Proportionate share of net assets of Euro Infrastructure Co.	129,491	127,393
Excess carrying value of investment over proportionate share of net assets	14,798	14,501
Euro Infrastructure Co [Member] | Goodwill [Member]
Schedule of Equity Method Investments [Line Items]
Excess carrying value of investment over proportionate share of net assets	21,214	20,791
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	12,626	12,379
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	(20,646)	(20,241)
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	$ 1,604	$ 1,572