Regulatory Capital (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings	$ 25,238	$ 23,442
Capital ratio: required common equity tier 1 capital	8.00%	8.00%
Capital ratio: required tier 1 capital	0.095	0.095
Capital ratio: required total capital	0.115	0.115
Tier 1 leverage capital ratio, minimum	0.040	0.040
Capital conservation buffer, capital conserved, minimum	0.025
Stress capital buffer, minimum	2.50%
Banking Regulation, Global Systemically Important Bank (GSIB) Surcharge	0.010
Countercyclical capital buffer	0
Leverage ratio minimum	0.05
Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 11,291	$ 10,709
Retained earnings	25,238	23,442
Accumulated other comprehensive income (loss)	(1,133)	187
Treasury stock, at cost	(10,009)	(10,609)
Total	25,387	23,729
Goodwill and other intangible assets, net of associated deferred tax liabilities	(8,935)	(9,019)
Other adjustments(1)	(505)	(333)
Common equity tier 1 capital	15,947	14,377
Preferred stock	1,976	2,471
Tier 1 capital	17,923	16,848
Qualifying subordinated long-term debt	1,588	961
Allowance for credit losses	0	1
Total capital	19,511	17,810
Credit risk	63,735	63,367
Operational risk	45,550	44,150
Market risk	2,113	2,188
Total risk-weighted assets	111,398	109,705
Adjusted quarterly average assets	$ 293,567	$ 263,490
Common equity tier 1 capital	14.30%	13.10%
Tier 1 capital	0.161	0.154
Total capital	0.175	0.162
Tier 1 leverage capital ratio, actual	0.061	0.064
Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 11,291	$ 10,709
Retained earnings	25,238	23,442
Accumulated other comprehensive income (loss)	(1,133)	187
Treasury stock, at cost		(10,609)
Total	25,387	23,729
Goodwill and other intangible assets, net of associated deferred tax liabilities	(8,935)	(9,019)
Other adjustments(1)	(505)	(333)
Common equity tier 1 capital	15,947	14,377
Preferred stock	1,976	2,471
Tier 1 capital	17,923	16,848
Qualifying subordinated long-term debt	1,588	961
Allowance for credit losses	108	148
Total capital	19,619	17,957
Credit risk	109,554	114,892
Market risk	2,113	2,188
Total risk-weighted assets	111,667	117,080
Adjusted quarterly average assets	$ 293,567	$ 263,490
Common equity tier 1 capital	14.30%	12.30%
Tier 1 capital	0.161	0.144
Total capital	0.176	0.153
Tier 1 leverage capital ratio, actual	0.061	0.064
State Street Bank | Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 13,047	$ 12,893
Retained earnings	15,700	12,939
Accumulated other comprehensive income (loss)	(926)	371
Treasury stock, at cost	0	0
Total	27,821	26,203
Goodwill and other intangible assets, net of associated deferred tax liabilities	(8,667)	(8,745)
Other adjustments(1)	(309)	(152)
Common equity tier 1 capital	18,845	17,306
Preferred stock	0	0
Tier 1 capital	18,845	17,306
Qualifying subordinated long-term debt	752	966
Allowance for credit losses	0	10
Total capital	19,597	18,282
Credit risk	57,405	58,960
Operational risk	42,813	43,663
Market risk	2,113	2,188
Total risk-weighted assets	102,331	104,811
Adjusted quarterly average assets	$ 290,403	$ 260,489
Common equity tier 1 capital	18.40%	16.50%
Tier 1 capital	0.184	0.165
Total capital	0.192	0.174
Tier 1 leverage capital ratio, actual	0.065	0.066
State Street Bank | Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 13,047	$ 12,893
Retained earnings	15,700	12,939
Accumulated other comprehensive income (loss)	(926)	371
Treasury stock, at cost	0	0
Total	27,821	26,203
Goodwill and other intangible assets, net of associated deferred tax liabilities	(8,667)	(8,745)
Other adjustments(1)	(309)	(152)
Common equity tier 1 capital	18,845	17,306
Preferred stock	0	0
Tier 1 capital	18,845	17,306
Qualifying subordinated long-term debt	752	966
Allowance for credit losses	108	148
Total capital	19,705	18,420
Credit risk	106,405	110,797
Market risk	2,113	2,188
Total risk-weighted assets	108,518	112,985
Adjusted quarterly average assets	$ 290,403	$ 260,489
Common equity tier 1 capital	17.40%	15.30%
Tier 1 capital	0.174	0.153
Total capital	0.182	0.163
Tier 1 leverage capital ratio, actual	0.065	0.066