Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2025		Mar. 31, 2024
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	$ 1,567		$ 1,468
Equity investments	3,014		3,037
Investments in marketable securities total	4,581		4,505
U.S. government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	743		697
Foreign government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	20		12
Municipal debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	8		7
Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	15
Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	450		430
U.S. government agency mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	141		118
Non-agency residential mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	11		11
Non-agency commercial mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	45		55
Asset-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	134		138
Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	1,567		1,468
Equity investments	3,014		3,037
Investments in marketable securities total	4,581		4,505
Derivative assets	46		41
Counterparty netting and collateral	(449)		(1,197)
Assets at fair value	4,627		4,546
Counterparty netting and collateral	721		947
Liabilities at fair value	(27)		(23)
Net assets at fair value	4,600		4,523
Recurring [Member] | U.S. government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	743		697
Recurring [Member] | Foreign government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	20		12
Recurring [Member] | Municipal debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	8		7
Recurring [Member] | Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	15
Recurring [Member] | Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	450		430
Recurring [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	141		118
Recurring [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	11		11
Recurring [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	45		55
Recurring [Member] | Asset-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	134		138
Recurring [Member] | Equity mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	1,147		1,073
Recurring [Member] | Fixed income total return bond funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	771		830
Recurring [Member] | Counterparty Netting & Collateral [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Equity investments	0		0
Investments in marketable securities total	0		0
Derivative assets	(449)		(1,197)
Counterparty netting and collateral	(449)		(1,197)
Assets at fair value	(449)		(1,197)
Counterparty netting and collateral	721		947
Liabilities at fair value	721		947
Net assets at fair value	272		(250)
Recurring [Member] | Counterparty Netting & Collateral [Member] | U.S. government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Foreign government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Municipal debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Asset-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Equity mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	0		0
Recurring [Member] | Counterparty Netting & Collateral [Member] | Fixed income total return bond funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	0		0
Recurring [Member] | Foreign currency swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	132		89
Derivative liabilities	(717)		(918)
Recurring [Member] | Foreign currency swaps [Member] | Counterparty Netting & Collateral [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities	0		0
Recurring [Member] | Interest rate swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	363		1,149
Derivative liabilities	(31)		(52)
Recurring [Member] | Interest rate swaps [Member] | Counterparty Netting & Collateral [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities	0		0
Recurring [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	724		693
Equity investments	1,918		1,903
Investments in marketable securities total	2,642		2,596
Derivative assets	0		0
Counterparty netting and collateral	0		0
Assets at fair value	2,642		2,596
Counterparty netting and collateral	0		0
Liabilities at fair value	0		0
Net assets at fair value	2,642		2,596
Recurring [Member] | Level 1 [Member] | U.S. government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	724		693
Recurring [Member] | Level 1 [Member] | Foreign government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 1 [Member] | Municipal debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 1 [Member] | Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0
Recurring [Member] | Level 1 [Member] | Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 1 [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 1 [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 1 [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 1 [Member] | Asset-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 1 [Member] | Equity mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	1,147		1,073
Recurring [Member] | Level 1 [Member] | Fixed income total return bond funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	771		830
Recurring [Member] | Level 1 [Member] | Foreign currency swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities	0		0
Recurring [Member] | Level 1 [Member] | Interest rate swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities	0		0
Recurring [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	771		706
Equity investments	0		0
Investments in marketable securities total	771		706
Derivative assets	495		1,238
Counterparty netting and collateral	0		0
Assets at fair value	1,266		1,944
Counterparty netting and collateral	0		0
Liabilities at fair value	(748)		(970)
Net assets at fair value	518		974
Recurring [Member] | Level 2 [Member] | U.S. government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	19		4
Recurring [Member] | Level 2 [Member] | Foreign government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	20		12
Recurring [Member] | Level 2 [Member] | Municipal debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	8		7
Recurring [Member] | Level 2 [Member] | Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	15
Recurring [Member] | Level 2 [Member] | Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	450		430
Recurring [Member] | Level 2 [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	141		118
Recurring [Member] | Level 2 [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	9		7
Recurring [Member] | Level 2 [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	44		46
Recurring [Member] | Level 2 [Member] | Asset-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	65		82
Recurring [Member] | Level 2 [Member] | Equity mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	0		0
Recurring [Member] | Level 2 [Member] | Fixed income total return bond funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	0		0
Recurring [Member] | Level 2 [Member] | Foreign currency swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	132		89
Derivative liabilities	(717)		(918)
Recurring [Member] | Level 2 [Member] | Interest rate swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	363		1,149
Derivative liabilities	(31)		(52)
Recurring [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	72		69
Equity investments	0		0
Investments in marketable securities total	72		69
Derivative assets	0		0
Counterparty netting and collateral	0		0
Assets at fair value	72		69
Counterparty netting and collateral	0		0
Liabilities at fair value	0		0
Net assets at fair value	72		69
Recurring [Member] | Level 3 [Member] | U.S. government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 3 [Member] | Foreign government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 3 [Member] | Municipal debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 3 [Member] | Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0
Recurring [Member] | Level 3 [Member] | Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 3 [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	0		0
Recurring [Member] | Level 3 [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	2		4
Recurring [Member] | Level 3 [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	1		9
Recurring [Member] | Level 3 [Member] | Asset-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Debt securities	69		56
Recurring [Member] | Level 3 [Member] | Equity mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	0		0
Recurring [Member] | Level 3 [Member] | Fixed income total return bond funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	0		0
Recurring [Member] | Level 3 [Member] | Foreign currency swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities	0		0
Recurring [Member] | Level 3 [Member] | Interest rate swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities	0		0
Recurring [Member] | Fixed income mutual funds measured at net asset value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	$ 1,096	[1]	$ 1,134	[2]

[1] 1. Measured at net asset value and therefore excluded from leveling.

[2] 1. Measured at net asset value and therefore excluded from leveling