Debt 3 (Details) - Revolving Credit Facility	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Rates applicable to revolving credit facility
Applicable margin on Base Rate borrowing	0.125%	0.125%
Weighted average interest rate on outstanding borrowings	0.00%	0.00%
Applicable margin on Eurocurrency Rate borrowing	1.00%	1.00%
Facility commitment fee	0.125%	0.125%