Expenses - Narrative (Details) - State Street Beacon - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2016
Restructuring Cost and Reserve [Line Items]
Accruals for State Street Beacon	$ 13	$ 97	$ 110
Employee Related Costs
Restructuring Cost and Reserve [Line Items]
Accruals for State Street Beacon	(1)	$ 86
Minimum
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost	300		300
Minimum | Employee Related Costs
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost	250		250
Minimum | Information Technology and Real Estate
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost	50		50
Maximum
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost	400		400
Maximum | Employee Related Costs
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost	300		300
Maximum | Information Technology and Real Estate
Restructuring Cost and Reserve [Line Items]
Expected restructuring cost	$ 100		$ 100