Debt and Credit Facilities - Debt and Related Weighted Average Contractual Interest Rates (Details) - USD ($) $ in Millions	Dec. 31, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Debt, Face value	$ 119,569	$ 112,170
Debt, Carrying value	$ 119,006	$ 111,685
Weighted average contractual interest rates	4.22%	3.56%
Unsecured notes and loans payable [Member]
Debt Instrument [Line Items]
Debt, Face value	$ 86,258	$ 79,393
Debt, Carrying value	$ 85,744	$ 78,949
Weighted average contractual interest rates	4.09%	3.48%
Secured notes and loans payable [Member]
Debt Instrument [Line Items]
Debt, Face value	$ 33,311	$ 32,777
Debt, Carrying value	$ 33,262	$ 32,736
Weighted average contractual interest rates	4.55%	3.76%