Ordinary and Preference Shares - Summary of Shares Issued and Outstanding (Parenthetical) (Detail)	9 Months Ended	12 Months Ended
Dec. 31, 2018	Mar. 31, 2018
Class Of Stock [Line Items]
Preference share dividend percentage	7.00%	7.00%
7% Cumulative Redeemable Preference Shares [Member]
Class Of Stock [Line Items]
Preference share dividend percentage	7.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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