Interest on Borrowings (Components of interest expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Interest expense, borrowings:
Interest expense	$ 106,221	$ 85,404	$ 80,905
Capitalized interest	(4,863)	(3,623)	(1,204)
Amortization of transaction costs	3,445	3,235	3,495
Interest expense resulting from derivatives	8,603	12,699	14,329
Total interest expense	113,406	97,715	97,525
Write-off of transaction costs related to early extinguishment of debt	499		298
Fees on early extinguishment of debt			3,783
Fees and amortization of early extinguishment of debt	499		4,081
Total	$ 113,905	$ 97,715	$ 101,606