Borrowings (Interest Rates and Company Borrowings) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Interest and debt expense:
Weighted average interest rate during the quarter	1.73%	1.63%	1.73%	1.64%
Interest rate at quarter end	1.73%	1.63%	1.73%	1.63%
Maximum amount outstanding during the quarter	$ 462,000	$ 250,000	$ 462,000	$ 250,000
Average amount outstanding during the period	431,815	234,348	400,896	207,678
Facility fees	$ 49	$ 50	$ 89	$ 144