Regulatory Capital (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Retained earnings	$ 16,686	$ 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	$ 10,271	$ 10,250
Retained earnings	16,686	16,049
Accumulated other comprehensive income (loss)	(1,124)	(1,422)
Treasury stock, at cost	(7,083)	(6,457)
Total	18,750	18,420
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,144)	(5,927)
Other adjustments	(88)	(60)
Common equity tier 1 capital	12,518	12,433
Preferred stock	3,196	2,703
Trust preferred capital securities subject to phase-out from tier 1 capital	0	237
Other adjustments	(72)	(109)
Tier 1 capital	15,642	15,264
Qualifying subordinated long-term debt	1,259	1,358
Trust preferred capital securities phased out of tier 1 capital	890	713
ALLL and other	3	12
Other adjustments	0	2
Total capital	17,794	17,349
Credit risk	55,748	51,733
Operational risk	44,436	43,882
Market risk	3,828	3,937
Total risk-weighted assets	104,012	99,552
Adjusted quarterly average assets	$ 222,666	$ 221,880
Common equity tier 1 capital	12.00%	12.50%
Tier 1 capital	15.00%	15.30%
Total capital	17.10%	17.40%
Tier 1 leveraged	7.00%	6.90%
Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,271	$ 10,250
Retained earnings	16,686	16,049
Accumulated other comprehensive income (loss)	(1,124)	(1,422)
Treasury stock, at cost	(7,083)	(6,457)
Total	18,750	18,420
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,144)	(5,927)
Other adjustments	(88)	(60)
Common equity tier 1 capital	12,518	12,433
Preferred stock	3,196	2,703
Trust preferred capital securities subject to phase-out from tier 1 capital	0	237
Other adjustments	(72)	(109)
Tier 1 capital	15,642	15,264
Qualifying subordinated long-term debt	1,259	1,358
Trust preferred capital securities phased out of tier 1 capital	890	713
ALLL and other	78	66
Other adjustments	0	2
Total capital	17,869	17,403
Credit risk	102,932	93,515
Market risk	1,560	2,378
Total risk-weighted assets	104,492	95,893
Adjusted quarterly average assets	$ 222,666	$ 221,880
Common equity tier 1 capital	12.00%	13.00%
Tier 1 capital	15.00%	15.90%
Total capital	17.10%	18.10%
Tier 1 leveraged	7.00%	6.90%
State Street Bank | Basel III Advanced Approaches
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,941	$ 10,938
Retained earnings	11,638	10,655
Accumulated other comprehensive income (loss)	(907)	(1,230)
Treasury stock, at cost	0	0
Total	21,672	20,363
Goodwill and other intangible assets, net of associated deferred tax liabilities	(5,844)	(5,631)
Other adjustments	(86)	(85)
Common equity tier 1 capital	15,742	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	15,742	14,647
Qualifying subordinated long-term debt	1,270	1,371
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	0	8
Other adjustments	0	0
Total capital	17,012	16,026
Credit risk	51,328	47,677
Operational risk	43,899	43,324
Market risk	3,831	3,939
Total risk-weighted assets	99,058	94,940
Adjusted quarterly average assets	$ 218,363	$ 217,358
Common equity tier 1 capital	15.90%	15.40%
Tier 1 capital	15.90%	15.40%
Total capital	17.20%	16.90%
Tier 1 leveraged	7.20%	6.70%
State Street Bank | Basel III Standardized Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	$ 10,941	$ 10,938
Retained earnings	11,638	10,655
Accumulated other comprehensive income (loss)	(907)	(1,230)
Treasury stock, at cost	0	0
Total	21,672	20,363
Goodwill and other intangible assets, net of associated deferred tax liabilities	(5,844)	(5,631)
Other adjustments	(86)	(85)
Common equity tier 1 capital	15,742	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	15,742	14,647
Qualifying subordinated long-term debt	1,270	1,371
Trust preferred capital securities phased out of tier 1 capital	0	0
ALLL and other	78	66
Other adjustments	0	0
Total capital	17,090	16,084
Credit risk	98,387	89,164
Market risk	1,560	2,378
Total risk-weighted assets	99,947	91,542
Adjusted quarterly average assets	$ 218,363	$ 217,358
Common equity tier 1 capital	15.80%	16.00%
Tier 1 capital	15.80%	16.00%
Total capital	17.10%	17.60%
Tier 1 leveraged	7.20%	6.70%