Regulatory Capital (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings	$ 17,762	$ 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	$ 10,300	$ 10,286
Retained earnings	17,762	17,459
Accumulated other comprehensive income (loss)	(1,782)	(1,936)
Treasury stock, at cost	(8,159)	(7,682)
Total	18,121	18,127
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,641)	(6,348)
Other adjustments	(161)	(155)
Common equity tier 1 capital	11,319	11,624
Preferred stock	3,196	3,196
Trust preferred capital securities subject to phase-out from tier 1 capital	0	0
Other adjustments	(40)	(103)
Tier 1 capital	14,475	14,717
Qualifying subordinated long-term debt	1,067	1,172
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	0	19
Other adjustments	0	1
Total capital	15,542	15,909
Credit risk	52,759	50,900
Operational risk(4)	44,798	44,579
Market risk	3,286	3,822
Total risk-weighted assets	100,843	99,301
Adjusted quarterly average assets	$ 212,361	$ 226,310
Common equity tier 1 capital	11.20%	11.70%
Tier 1 capital	14.40%	14.80%
Total capital	15.40%	16.00%
Tier 1 leveraged	6.80%	6.50%
Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,300	$ 10,286
Retained earnings	17,762	17,459
Accumulated other comprehensive income (loss)	(1,782)	(1,936)
Treasury stock, at cost	(8,159)	(7,682)
Total	18,121	18,127
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,641)	(6,348)
Other adjustments	(161)	(155)
Common equity tier 1 capital	11,319	11,624
Preferred stock	3,196	3,196
Trust preferred capital securities subject to phase-out from tier 1 capital	0	0
Other adjustments	(40)	(103)
Tier 1 capital	14,475	14,717
Qualifying subordinated long-term debt	1,067	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	15,617	15,967
Credit risk	96,948	98,125
Market risk	1,546	1,751
Total risk-weighted assets	98,494	99,876
Adjusted quarterly average assets	$ 212,361	$ 226,310
Common equity tier 1 capital	11.50%	11.60%
Tier 1 capital	14.70%	14.70%
Total capital	15.90%	16.00%
Tier 1 leveraged	6.80%	6.50%
State Street Bank | Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 11,376	$ 11,376
Retained earnings	12,089	12,285
Accumulated other comprehensive income (loss)	(1,530)	(1,648)
Treasury stock, at cost	0	0
Total	21,935	22,013
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,349)	(6,060)
Other adjustments	(94)	(148)
Common equity tier 1 capital	15,492	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	15,492	15,805
Qualifying subordinated long-term debt	1,072	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	16,564	16,999
Credit risk	49,492	47,383
Operational risk(4)	44,256	44,043
Market risk	3,286	3,822
Total risk-weighted assets	97,034	95,248
Adjusted quarterly average assets	$ 209,392	$ 222,584
Common equity tier 1 capital	16.00%	16.60%
Tier 1 capital	16.00%	16.60%
Total capital	17.10%	17.80%
Tier 1 leveraged	7.40%	7.10%
State Street Bank | Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 11,376	$ 11,376
Retained earnings	12,089	12,285
Accumulated other comprehensive income (loss)	(1,530)	(1,648)
Treasury stock, at cost	0	0
Total	21,935	22,013
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,349)	(6,060)
Other adjustments	(94)	(148)
Common equity tier 1 capital	15,492	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	15,492	15,805
Qualifying subordinated long-term debt	1,072	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	16,639	17,061
Credit risk	93,501	94,413
Market risk	1,546	1,751
Total risk-weighted assets	95,047	96,164
Adjusted quarterly average assets	$ 209,392	$ 222,584
Common equity tier 1 capital	16.30%	16.40%
Tier 1 capital	16.30%	16.40%
Total capital	17.50%	17.70%
Tier 1 leveraged	7.40%	7.10%