Related Party Transactions (Related Party Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Related party transactions:
Management fee revenue	$ 8,765	$ 9,098	$ 23,952	$ 23,487
Revenue from related parties	8,765	9,098	23,952	23,487
Blackwater [Member]
Related party transactions:
Management fee revenue	6,350	5,763	19,142	18,330
Mercury [Member]
Related party transactions:
Management fee revenue	$ 2,415	$ 3,335	$ 4,810	$ 5,157