Regulatory Capital (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings	$ 18,202	$ 17,459
Capital ratio: required common equity tier 1 capital	6.50%	5.50%
Capital ratio: required tier 1 capital	8.00%	7.00%
Capital ratio: required total capital	10.00%	9.00%
Capital ratio: required tier 1 leverage	4.00%	4.00%
Percentage of goodwill and other intangible assets net of associated deferred tax liabilities allocated to other intangible assets	80.00%	60.00%
Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,307	$ 10,286
Retained earnings	18,202	17,459
Accumulated other comprehensive income (loss)	(1,266)	(1,936)
Treasury stock, at cost	(8,367)	(7,682)
Total	18,876	18,127
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,714)	(6,348)
Other adjustments	(155)	(155)
Common equity tier 1 capital	12,007	11,624
Preferred stock	3,196	3,196
Trust preferred capital securities subject to phase-out from tier 1 capital	0	0
Other adjustments	(38)	(103)
Tier 1 capital	15,165	14,717
Qualifying subordinated long-term debt	1,074	1,172
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	4	19
Other adjustments	0	1
Total capital	16,243	15,909
Credit risk	52,755	50,900
Operational risk(4)	44,123	44,579
Market risk	3,387	3,822
Total risk-weighted assets	100,265	99,301
Adjusted quarterly average assets	$ 216,940	$ 226,310
Common equity tier 1 capital	12.00%	11.70%
Tier 1 capital	15.10%	14.80%
Total capital	16.20%	16.00%
Tier 1 leveraged	7.00%	6.50%
Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,307	$ 10,286
Retained earnings	18,202	17,459
Accumulated other comprehensive income (loss)	(1,266)	(1,936)
Treasury stock, at cost	(8,367)	(7,682)
Total	18,876	18,127
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,714)	(6,348)
Other adjustments	(155)	(155)
Common equity tier 1 capital	12,007	11,624
Preferred stock	3,196	3,196
Trust preferred capital securities subject to phase-out from tier 1 capital	0	0
Other adjustments	(38)	(103)
Tier 1 capital	15,165	14,717
Qualifying subordinated long-term debt	1,074	1,172
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	75	77
Other adjustments	0	1
Total capital	16,314	15,967
Credit risk	105,785	98,125
Market risk	1,284	1,751
Total risk-weighted assets	107,069	99,876
Adjusted quarterly average assets	$ 216,940	$ 226,310
Common equity tier 1 capital	11.20%	11.60%
Tier 1 capital	14.20%	14.70%
Total capital	15.20%	16.00%
Tier 1 leveraged	7.00%	6.50%
State Street Bank | Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 11,382	$ 11,376
Retained earnings	12,188	12,285
Accumulated other comprehensive income (loss)	(1,060)	(1,648)
Treasury stock, at cost	0	0
Total	22,510	22,013
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,417)	(6,060)
Other adjustments	(91)	(148)
Common equity tier 1 capital	16,002	15,805
Preferred stock	0	0
Trust preferred capital securities subject to phase-out from tier 1 capital	0	0
Other adjustments	0	0
Tier 1 capital	16,002	15,805
Qualifying subordinated long-term debt	1,078	1,179
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	0	15
Other adjustments	0	0
Total capital	17,080	16,999
Credit risk	50,010	47,383
Operational risk(4)	43,552	44,043
Market risk	3,388	3,822
Total risk-weighted assets	96,950	95,248
Adjusted quarterly average assets	$ 214,022	$ 222,584
Common equity tier 1 capital	16.50%	16.60%
Tier 1 capital	16.50%	16.60%
Total capital	17.60%	17.80%
Tier 1 leveraged	7.50%	7.10%
State Street Bank | Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 11,382	$ 11,376
Retained earnings	12,188	12,285
Accumulated other comprehensive income (loss)	(1,060)	(1,648)
Treasury stock, at cost	0	0
Total	22,510	22,013
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,417)	(6,060)
Other adjustments	(91)	(148)
Common equity tier 1 capital	16,002	15,805
Preferred stock	0	0
Trust preferred capital securities subject to phase-out from tier 1 capital	0	0
Other adjustments	0	0
Tier 1 capital	16,002	15,805
Qualifying subordinated long-term debt	1,078	1,179
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	75	77
Other adjustments	0	0
Total capital	17,155	17,061
Credit risk	102,642	94,413
Market risk	1,284	1,751
Total risk-weighted assets	103,926	96,164
Adjusted quarterly average assets	$ 214,022	$ 222,584
Common equity tier 1 capital	15.40%	16.40%
Tier 1 capital	15.40%	16.40%
Total capital	16.50%	17.70%
Tier 1 leveraged	7.50%	7.10%