Variable Interest Entities - Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Variable Interest Entity [Line Items]
Investment in variable interest entities	$ 69,243	$ 69,459	$ 62,838
Advances to variable interest entities	9,800	5,783	3,587
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Investment in variable interest entities	62,468	64,281	57,251
Advances to variable interest entities	7,486	3,273	994
Guaranteed amounts to variable interest entities (not to exceed)	$ 66,375	$ 67,027	$ 73,696