Fair Value Measurements - Summary of Fair Value Hierarchy of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 31, 2025	Mar. 31, 2024
Derivative instruments:
Total assets	$ 389	$ 743
Total liabilities	1,120	1,472
Level 1
Derivative instruments:
Total assets	0	0
Total liabilities	0	0
Level 2
Derivative instruments:
Total assets	389	743
Total liabilities	1,120	1,472
Level 3
Derivative instruments:
Total assets	0	0
Total liabilities	0	0
Interest rate swaps
Derivative instruments:
Total assets	338	714
Total liabilities	676	881
Interest rate swaps \| Level 1
Derivative instruments:
Total assets	0	0
Total liabilities	0	0
Interest rate swaps \| Level 2
Derivative instruments:
Total assets	338	714
Total liabilities	676	881
Interest rate swaps \| Level 3
Derivative instruments:
Total assets	0	0
Total liabilities	0	0
Cross currency swaps
Derivative instruments:
Total assets	51	29
Total liabilities	444	591
Cross currency swaps \| Level 1
Derivative instruments:
Total assets	0	0
Total liabilities	0	0
Cross currency swaps \| Level 2
Derivative instruments:
Total assets	51	29
Total liabilities	444	591
Cross currency swaps \| Level 3
Derivative instruments:
Total assets	0	0
Total liabilities	$ 0	$ 0