Expenses - Restructuring Reserve (Details) - USD ($)	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Restructuring Reserve [Roll Forward]
Beginning balance	$ 209,000,000	$ 259,000,000	$ 341,000,000	$ 213,000,000	$ 175,000,000	$ 201,000,000
Accruals	0			0	77,000,000
Payments and other adjustments	(64,000,000)	(52,000,000)	(78,000,000)	(23,000,000)	(39,000,000)	(26,000,000)
Ending balance	145,000,000	209,000,000	259,000,000	189,000,000	213,000,000	175,000,000
Employee Related Costs
Restructuring Reserve [Roll Forward]
Beginning balance	197,000,000	246,000,000	303,000,000	169,000,000	144,000,000	166,000,000
Accruals					61,000,000
Payments and other adjustments	(62,000,000)	(51,000,000)	(53,000,000)	(18,000,000)	(36,000,000)	(22,000,000)
Ending balance	135,000,000	197,000,000	246,000,000	150,000,000	169,000,000	144,000,000
Real Estate Actions
Restructuring Reserve [Roll Forward]
Beginning balance	11,000,000	12,000,000	37,000,000	41,000,000	28,000,000	32,000,000
Accruals					16,000,000
Payments and other adjustments	(2,000,000)	(1,000,000)	(25,000,000)	(4,000,000)	(3,000,000)	(4,000,000)
Ending balance	9,000,000	11,000,000	12,000,000	37,000,000	41,000,000	28,000,000
Asset and Other Write-offs
Restructuring Reserve [Roll Forward]
Beginning balance	1,000,000	1,000,000	1,000,000	3,000,000	3,000,000	3,000,000
Accruals					0
Payments and other adjustments	0	0	0	(1,000,000)	0	0
Ending balance	$ 1,000,000	1,000,000	1,000,000	2,000,000	$ 3,000,000	$ 3,000,000
State Street Beacon
Restructuring Reserve [Roll Forward]
Accruals		2,000,000	(4,000,000)	(1,000,000)
State Street Beacon | Employee Related Costs
Restructuring Reserve [Roll Forward]
Accruals		2,000,000	(4,000,000)	(1,000,000)
State Street Beacon | Real Estate Actions
Restructuring Reserve [Roll Forward]
Accruals		0	0	0
State Street Beacon | Asset and Other Write-offs
Restructuring Reserve [Roll Forward]
Accruals		$ 0	$ 0	$ 0