Ordinary and Preference Shares - Summary of Shares Issued and Outstanding (Parenthetical) (Detail)	6 Months Ended	12 Months Ended
Sep. 30, 2017	Mar. 31, 2017
7% Cumulative Redeemable Preference Shares [Member]
Class Of Stock [Line Items]
Dividend percentage	7.00%	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.

No definition available.

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