Regulatory Capital (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings	$ 17,459	$ 16,049
Capital ratio: required common equity tier 1 capital	5.50%	4.50%
Capital ratio: required tier 1 capital	7.00%	6.00%
Capital ratio: required total capital	9.00%	8.00%
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	60.00%	40.00%
Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,286	$ 10,250
Retained earnings	17,459	16,049
Accumulated other comprehensive income (loss)	(1,936)	(1,422)
Treasury stock, at cost	(7,682)	(6,457)
Total	18,127	18,420
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,348)	(5,927)
Other adjustments	(155)	(60)
Common equity tier 1 capital	11,624	12,433
Preferred stock	3,196	2,703
Trust preferred capital securities subject to phase-out from tier 1 capital	0	237
Other adjustments	(103)	(109)
Tier 1 capital	14,717	15,264
Qualifying subordinated long-term debt	1,172	1,358
Trust preferred capital securities phased out of tier 1 capital	0	713
ALLL and other	19	12
Other adjustments	1	2
Total capital	15,909	17,349
Credit risk	50,900	51,733
Operational risk(4)	44,579	43,882
Market risk	3,822	3,937
Total risk-weighted assets	99,301	99,552
Adjusted quarterly average assets	$ 226,310	$ 221,880
Common equity tier 1 capital	11.70%	12.50%
Tier 1 capital	14.80%	15.30%
Total capital	16.00%	17.40%
Tier 1 leveraged	6.50%	6.90%
Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,286	$ 10,250
Retained earnings	17,459	16,049
Accumulated other comprehensive income (loss)	(1,936)	(1,422)
Treasury stock, at cost	(7,682)	(6,457)
Total	18,127	18,420
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,348)	(5,927)
Other adjustments	(155)	(60)
Common equity tier 1 capital	11,624	12,433
Preferred stock	3,196	2,703
Trust preferred capital securities subject to phase-out from tier 1 capital	0	237
Other adjustments	(103)	(109)
Tier 1 capital	14,717	15,264
Qualifying subordinated long-term debt	1,172	1,358
Trust preferred capital securities phased out of tier 1 capital	0	713
ALLL and other	77	66
Other adjustments	1	2
Total capital	15,967	17,403
Credit risk	98,125	93,515
Market risk	1,751	2,378
Total risk-weighted assets	99,876	95,893
Adjusted quarterly average assets	$ 226,310	$ 221,880
Common equity tier 1 capital	11.60%	13.00%
Tier 1 capital	14.70%	15.90%
Total capital	16.00%	18.10%
Tier 1 leveraged	6.50%	6.90%
State Street Bank | Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 11,376	$ 10,938
Retained earnings	12,285	10,655
Accumulated other comprehensive income (loss)	(1,648)	(1,230)
Treasury stock, at cost	0	0
Total	22,013	20,363
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,060)	(5,631)
Other adjustments	(148)	(85)
Common equity tier 1 capital	15,805	14,647
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	15,805	14,647
Qualifying subordinated long-term debt	1,179	1,371
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	15	8
Other adjustments	0	0
Total capital	16,999	16,026
Credit risk	47,383	47,677
Operational risk(4)	44,043	43,324
Market risk	3,822	3,939
Total risk-weighted assets	95,248	94,940
Adjusted quarterly average assets	$ 222,584	$ 217,358
Common equity tier 1 capital	16.60%	15.40%
Tier 1 capital	16.60%	15.40%
Total capital	17.80%	16.90%
Tier 1 leveraged	7.10%	6.70%
State Street Bank | Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 11,376	$ 10,938
Retained earnings	12,285	10,655
Accumulated other comprehensive income (loss)	(1,648)	(1,230)
Treasury stock, at cost	0	0
Total	22,013	20,363
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,060)	(5,631)
Other adjustments	(148)	(85)
Common equity tier 1 capital	15,805	14,647
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	15,805	14,647
Qualifying subordinated long-term debt	1,179	1,371
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	77	66
Other adjustments	0	0
Total capital	17,061	16,084
Credit risk	94,413	89,164
Market risk	1,751	2,378
Total risk-weighted assets	96,164	91,542
Adjusted quarterly average assets	$ 222,584	$ 217,358
Common equity tier 1 capital	16.40%	16.00%
Tier 1 capital	16.40%	16.00%
Total capital	17.70%	17.60%
Tier 1 leveraged	7.10%	6.70%