Consolidated Statements of Financial Position (Parenthetical) $ in Millions	Sep. 30, 2025 USD ($) $ / shares shares	Sep. 30, 2025 € / shares	Sep. 30, 2024 USD ($) $ / shares shares	Sep. 30, 2024 € / shares
Allowance for expected credit losses | $	$ 205		$ 210
Ordinary shares, par value (in dollars per share) | $ / shares	$ 0.01		$ 0.01
Ordinary shares authorized (in shares)	2,000,000,000.0		2,000,000,000.0
Ordinary shares issued (in shares)	641,632,294		692,964,542
Preferred shares, par or stated value per share (in dollars per share) | $ / shares	$ 0.01		$ 0.01
Preferred shares authorized (in shares)	200,000,000		200,000,000
Preferred shares outstanding (in shares)	0		0
Ordinary shares held in treasury (in shares)	30,501,903		30,086,539
Common Class A
Ordinary shares, par value (in dollars per share) | € / shares		€ 1.00		€ 1.00
Ordinary shares authorized (in shares)	40,000		40,000
Ordinary shares outstanding (in shares)	0		0