Segment Information (Net Revenue By Geographic Area) (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Revenue from External Customer [Line Items]
Net revenue	$ 5,629	$ 5,537	$ 4,950
North America [Member]
Revenue from External Customer [Line Items]
Net revenue	2,474	2,270	1,906
International [Member]
Revenue from External Customer [Line Items]
Net revenue	$ 3,155	$ 3,267	$ 3,044

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ Details