Borrowings (Interest Rates and Company Borrowings) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Interest and debt expense:
Weighted average interest rate during the quarter	3.09%	3.52%	3.44%	3.31%
Interest rate at quarter end	2.95%	3.57%	2.95%	3.57%
Maximum amount outstanding during the quarter	$ 1,025,000	$ 865,000	$ 1,025,000	$ 865,000
Average amount outstanding during the quarter	1,014,511	812,174	995,508	632,509
Facility fees	$ 40	$ 41	$ 147	$ 313