Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020
Statement Of Financial Position [Abstract]
Finance receivables, allowance for credit losses	$ 1,104	$ 727
Common Stock, Par or Stated Value Per Share
Common Stock, Shares Authorized	100,000	100,000
Common Stock, Shares, Issued	91,500	91,500
Common Stock, Shares, Outstanding	91,500	91,500