Fair Value Measurements - Summary of Fair Value Hierarchy of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Jun. 30, 2026	Mar. 31, 2026
Derivative instruments:
Derivative instruments	$ 544	$ 569
Total assets	544	569
Derivative instruments	604	661
Total liabilities	604	661
Level 1
Derivative instruments:
Total assets	0	0
Total liabilities	0	0
Level 2
Derivative instruments:
Total assets	544	569
Total liabilities	604	661
Level 3
Derivative instruments:
Total assets	0	0
Total liabilities	0	0
Interest rate swaps
Derivative instruments:
Derivative instruments	330	228
Derivative instruments	370	442
Interest rate swaps \| Level 1
Derivative instruments:
Derivative instruments	0	0
Derivative instruments	0	0
Interest rate swaps \| Level 2
Derivative instruments:
Derivative instruments	330	228
Derivative instruments	370	442
Interest rate swaps \| Level 3
Derivative instruments:
Derivative instruments	0	0
Derivative instruments	0	0
Cross currency swaps
Derivative instruments:
Derivative instruments	214	341
Derivative instruments	234	219
Cross currency swaps \| Level 1
Derivative instruments:
Derivative instruments	0	0
Derivative instruments	0	0
Cross currency swaps \| Level 2
Derivative instruments:
Derivative instruments	214	341
Derivative instruments	234	219
Cross currency swaps \| Level 3
Derivative instruments:
Derivative instruments	0	0
Derivative instruments	$ 0	$ 0