Variable Interest Entities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Variable Interest Entity [Line Items]
VIE consolidated assets	$ 65,015	$ 61,247
Unconsolidated VIE maximum exposure to loss	1,500	1,400
Consolidated Variable Interest Entities
Variable Interest Entity [Line Items]
VIE consolidated assets	662	695
VIE consolidated liabilities	$ 74	$ 82