Segment Information - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Unearned amounts in voluntary protection contract revenues, recognized	$ 696
Other liabilities [Member]
Segment Reporting Information [Line Items]
Unearned voluntary protection contract revenues	$ 2,500	$ 2,400
Accounting Standards Update 2014-09 [Member]
Segment Reporting Information [Line Items]
Percentage of voluntary protection contract revenues	83.00%	84.00%
Minimum [Member]
Segment Reporting Information [Line Items]
Insurance Policy Term	3 months
Maximum [Member]
Segment Reporting Information [Line Items]
Insurance Policy Term	120 months