U.S. and Europe Retrospective Responsibility Plan - Changes in the U.S. Litigation Escrow Account (Detail) - USD ($) $ in Millions		9 Months Ended
	Dec. 27, 2019	Jun. 30, 2020	Jun. 30, 2019
Escrow Account [Roll Forward]
Beginning balance		$ 1,205	$ 1,491
Return of takedown payment to the litigation escrow account	$ 467	467	0
Payments to class plaintiffs’ settlement fund		0	(600)
Ending balance		1,148	902
Interest Income | Opt-out Merchants
Escrow Account [Roll Forward]
Payments to opt-out merchants and interest earned on escrow funds		$ (524)	$ 11