Basis of Presentation and Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Apr. 01, 2020
Summary Of Significant Accounting Policies [Line Items]
Retained earnings	$ 17,205	$ 14,670
Allowance for credit losses	$ 1,246	$ 1,178
ASU 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adoption date			Apr. 01, 2020
Change in accounting principle, accounting standards update, adopted [true false]			true
Change in accounting principle, accounting standards update, immaterial effect [true false]			false
Accounting Standards Update 2020-04 [Member]
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adoption date	Apr. 01, 2021
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update, immaterial effect [true false]	false
Accounting Standards Update 2020-08 [Member]
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adoption date	Apr. 01, 2021
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update, immaterial effect [true false]	false
Cumulative Effect Period of Adoption Adjustment | ASU 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
Retained earnings			$ 218
Allowance for credit losses			292
Accrued interest			$ 190
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Finance Operations [Member] | California [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration Percentage	22.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Finance Operations [Member] | Texas [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration Percentage	12.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Finance Operations [Member] | New York [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration Percentage	7.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Finance Operations [Member] | New Jersey [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration Percentage	5.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Voluntary Protection Operations [Member] | California [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration Percentage	25.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Voluntary Protection Operations [Member] | New York [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration Percentage	6.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Voluntary Protection Operations [Member] | Maryland [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration Percentage	5.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Voluntary Protection Operations [Member] | Virginia [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration Percentage	5.00%