Expenses - Restructuring Reserve (Details) - USD ($)	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018
Restructuring Reserve [Roll Forward]
Beginning balance	$ 259,000,000	$ 341,000,000	$ 175,000,000	$ 201,000,000
Accruals	0		77,000,000
Payments and other adjustments	(52,000,000)	(78,000,000)	(39,000,000)	(26,000,000)
Ending balance	209,000,000	259,000,000	213,000,000	175,000,000
Employee Related Costs
Restructuring Reserve [Roll Forward]
Beginning balance	246,000,000	303,000,000	144,000,000	166,000,000
Accruals			61,000,000
Payments and other adjustments	(51,000,000)	(53,000,000)	(36,000,000)	(22,000,000)
Ending balance	197,000,000	246,000,000	169,000,000	144,000,000
Real Estate Actions
Restructuring Reserve [Roll Forward]
Beginning balance	12,000,000	37,000,000	28,000,000	32,000,000
Accruals			16,000,000
Payments and other adjustments	(1,000,000)	(25,000,000)	(3,000,000)	(4,000,000)
Ending balance	11,000,000	12,000,000	41,000,000	28,000,000
Asset and Other Write-offs
Restructuring Reserve [Roll Forward]
Beginning balance	1,000,000	1,000,000	3,000,000	3,000,000
Accruals			0
Payments and other adjustments	0	0	0	0
Ending balance	1,000,000	1,000,000	$ 3,000,000	$ 3,000,000
State Street Beacon
Restructuring Reserve [Roll Forward]
Accruals	2,000,000	(4,000,000)
State Street Beacon | Employee Related Costs
Restructuring Reserve [Roll Forward]
Accruals	2,000,000	(4,000,000)
State Street Beacon | Real Estate Actions
Restructuring Reserve [Roll Forward]
Accruals	0	0
State Street Beacon | Asset and Other Write-offs
Restructuring Reserve [Roll Forward]
Accruals	$ 0	$ 0