Interest on Borrowings (Components of interest expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Interest expense, borrowings:
Interest expense	$ 150,609	$ 125,412	$ 106,221
Capitalized interest	(12,733)	(6,466)	(4,863)
Amortization of transaction costs	3,745	3,867	3,445
Interest expense resulting from derivatives	824	3,893	8,603
Total interest expense	142,445	126,706	113,406
Amortization on early extinguishment of debt			499
Total	$ 142,445	$ 126,706	$ 113,905