Regulatory Capital (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings	$ 21,918	$ 20,553
Capital ratio: required common equity tier 1 capital	8.50%	7.50%
Capital ratio: required tier 1 capital	10.00%	9.00%
Capital ratio: required total capital	12.00%	11.00%
Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,636	$ 10,565
Retained earnings	21,918	20,606
Accumulated other comprehensive income (loss)	(870)	(1,332)
Treasury stock, at cost	(10,209)	(8,715)
Total	21,475	21,124
Goodwill and other intangible assets, net of associated deferred tax liabilities	(9,112)	(9,350)
Other adjustments	(150)	(194)
Common equity tier 1 capital	12,213	11,580
Preferred stock	2,962	3,690
Tier 1 capital	15,175	15,270
Qualifying subordinated long-term debt	1,095	778
Allowance for loan losses and other	5	14
Total capital	16,275	16,062
Credit risk	54,763	47,738
Operational risk	47,963	46,060
Market risk	1,638	1,517
Total risk-weighted assets	104,364	95,315
Adjusted quarterly average assets	$ 219,624	$ 211,924
Common equity tier 1 capital	11.70%	12.10%
Tier 1 capital	14.50%	16.00%
Total capital	15.60%	16.90%
Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,636	$ 10,565
Retained earnings	21,918	20,606
Accumulated other comprehensive income (loss)	(870)	(1,332)
Treasury stock, at cost	(10,209)	(8,715)
Total	21,475	21,124
Goodwill and other intangible assets, net of associated deferred tax liabilities	(9,112)	(9,350)
Other adjustments	(150)	(194)
Common equity tier 1 capital	12,213	11,580
Preferred stock	2,962	3,690
Tier 1 capital	15,175	15,270
Qualifying subordinated long-term debt	1,095	778
Allowance for loan losses and other	90	83
Total capital	16,360	16,131
Credit risk	102,367	97,303
Market risk	1,638	1,517
Total risk-weighted assets	104,005	98,820
Adjusted quarterly average assets	$ 219,624	$ 211,924
Common equity tier 1 capital	11.70%	11.70%
Tier 1 capital	14.60%	15.50%
Total capital	15.70%	16.30%
State Street Bank | Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 12,893	$ 12,894
Retained earnings	13,218	14,261
Accumulated other comprehensive income (loss)	(654)	(1,112)
Treasury stock, at cost	0	0
Total	25,457	26,043
Goodwill and other intangible assets, net of associated deferred tax liabilities	(8,839)	(9,073)
Other adjustments	(1)	(29)
Common equity tier 1 capital	16,617	16,941
Preferred stock	0	0
Tier 1 capital	16,617	16,941
Qualifying subordinated long-term debt	1,099	776
Allowance for loan losses and other	3	11
Total capital	17,719	17,728
Credit risk	51,610	45,565
Operational risk	44,138	44,494
Market risk	1,638	1,517
Total risk-weighted assets	97,386	91,576
Adjusted quarterly average assets	$ 216,397	$ 209,413
Common equity tier 1 capital	17.10%	18.50%
Tier 1 capital	17.10%	18.50%
Total capital	18.20%	19.40%
State Street Bank | Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 12,893	$ 12,894
Retained earnings	13,218	14,261
Accumulated other comprehensive income (loss)	(654)	(1,112)
Treasury stock, at cost	0	0
Total	25,457	26,043
Goodwill and other intangible assets, net of associated deferred tax liabilities	(8,839)	(9,073)
Other adjustments	(1)	(29)
Common equity tier 1 capital	16,617	16,941
Preferred stock	0	0
Tier 1 capital	16,617	16,941
Qualifying subordinated long-term debt	1,099	776
Allowance for loan losses and other	90	83
Total capital	17,806	17,800
Credit risk	98,979	94,776
Market risk	1,638	1,517
Total risk-weighted assets	100,617	96,293
Adjusted quarterly average assets	$ 216,397	$ 209,413
Common equity tier 1 capital	16.50%	17.60%
Tier 1 capital	16.50%	17.60%
Total capital	17.70%	18.50%