Borrowings (Interest Rates and Company Borrowings) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Interest and debt expense:
Weighted average interest rate during the quarter	3.52%	2.47%	3.31%	2.38%
Interest rate at quarter end	3.57%	2.56%	3.57%	2.56%
Maximum amount outstanding during the quarter	$ 865,000	$ 535,000	$ 865,000	$ 538,000
Average amount outstanding during the period	812,174	532,261	632,509	516,349
Facility fees	$ 41	$ 159	$ 313	$ 284