Expenses - Restructuring Reserve (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restructuring Reserve [Roll Forward]
Beginning balance	$ 341,000,000	$ 201,000,000
Payments and Other Adjustments	(78,000,000)	(26,000,000)
Ending balance	259,000,000	175,000,000
Employee Related Costs
Restructuring Reserve [Roll Forward]
Beginning balance	303,000,000	166,000,000
Payments and Other Adjustments	(53,000,000)	(22,000,000)
Ending balance	246,000,000	144,000,000
Real Estate Actions
Restructuring Reserve [Roll Forward]
Beginning balance	37,000,000	32,000,000
Payments and Other Adjustments	(25,000,000)	(4,000,000)
Ending balance	12,000,000	28,000,000
Asset and Other Write-offs
Restructuring Reserve [Roll Forward]
Beginning balance	1,000,000	3,000,000
Payments and Other Adjustments	0	0
Ending balance	1,000,000	3,000,000
State Street Beacon
Restructuring Reserve [Roll Forward]
Accruals	(4,000,000)	0
State Street Beacon | Employee Related Costs
Restructuring Reserve [Roll Forward]
Accruals	(4,000,000)	0
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