Regulatory Capital (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus			$ 10,280	[1]
Retained earnings	14,531		13,395	[1]
Accumulated other comprehensive income (loss)			215	[1]
Treasury Stock Value, Excluding Preferred Shares			3,693	[1]
Total shareholders’ equity			20,197	[1]
Goodwill and other intangible assets, net of associated deferred tax liabilities			(7,743)	[1],[2]
Other adjustments, common tier calculation			0	[1]
Tier one common risk-based capital			12,454	[1]
Preferred stock			491	[1]
Trust preferred capital securities subject to phase-out from tier 1 capital			950
Other adjustments, tier 1 risk based calculation			0	[1]
Tier One Risk Based Capital			13,895	[1]
Total Capital Qualifying Subordinated Long-Term Debt			1,918	[1]
Other adjustments, total capital calculation			(26)	[1]
Capital			15,787	[1]
Risk-weighted assets - credit risk			78,864	[1]
Risk-weighted assets - market risk			1,262	[1]
Total risk-weighted assets			80,126	[1]
Adjusted Quarterly Average Assets			202,801	[1]
Tier One Common Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.00%	[3]
Tier 1 common risk-based capital			15.50%	[1]
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	5.50%	[3]	4.00%	[4]
Tier 1 risk-based capital			17.30%	[1]
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	[3]	8.00%	[4]
Total risk-based capital			19.70%	[1]
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	[3]	4.00%	[4]
Tier 1 leverage			6.90%	[1]
Basel III Advanced Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	10,284	[5]
Retained earnings	14,531	[5]
Accumulated other comprehensive income (loss)	(264)	[5]
Treasury Stock Value, Excluding Preferred Shares	4,785	[1]
Total shareholders’ equity	19,766	[5]
Goodwill and other intangible assets, net of associated deferred tax liabilities	(5,942)	[2],[5]
Other adjustments, common tier calculation	(43)	[5]
Tier one common risk-based capital	13,781	[5]
Preferred stock	1,233	[5]
Trust preferred capital securities subject to phase-out from tier 1 capital	475	[5]
Other adjustments, tier 1 risk based calculation	(171)	[5]
Tier One Risk Based Capital	15,318	[5]
Total Capital Qualifying Subordinated Long-Term Debt	1,738	[1]
Trust preferred capital securities phased out of tier 1 capital	475	[5]
Other adjustments, total capital calculation	3	[5]
Capital	17,534	[5]
Risk-weighted assets - credit risk	67,915	[5]
Risk-weighted assets - operational risk	35,960	[5]
Risk-weighted assets - market risk	4,203	[5]
Total risk-weighted assets	108,078	[5]
Adjusted Quarterly Average Assets	240,529	[5]
Tier 1 common risk-based capital	12.80%	[5]
Tier 1 risk-based capital	14.20%	[5]
Total risk-based capital	16.20%	[5]
Tier 1 leverage	6.40%	[5]
Basel III Transitional Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	10,284	[6]
Retained earnings	14,531	[6]
Accumulated other comprehensive income (loss)	(264)	[6]
Treasury Stock Value, Excluding Preferred Shares	4,785	[1]
Total shareholders’ equity	19,766	[6]
Goodwill and other intangible assets, net of associated deferred tax liabilities	(5,942)	[2],[6]
Other adjustments, common tier calculation	(43)	[6]
Tier one common risk-based capital	13,781	[6]
Preferred stock	1,233	[6]
Trust preferred capital securities subject to phase-out from tier 1 capital	475	[6]
Other adjustments, tier 1 risk based calculation	(171)	[6]
Tier One Risk Based Capital	15,318	[6]
Total Capital Qualifying Subordinated Long-Term Debt	1,738	[1]
Trust preferred capital securities phased out of tier 1 capital	475	[6]
Other adjustments, total capital calculation	3	[6]
Capital	17,534	[6]
Risk-weighted assets - credit risk	90,377	[6]
Risk-weighted assets - market risk	1,423	[6]
Total risk-weighted assets	91,800	[6]
Adjusted Quarterly Average Assets	240,529	[6]
Tier 1 common risk-based capital	15.00%	[6]
Tier 1 risk-based capital	16.70%	[6]
Total risk-based capital	19.10%	[6]
Tier 1 leverage	6.40%	[6]
State Street Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus			10,786	[1]
Retained earnings			9,064	[1]
Accumulated other comprehensive income (loss)			209	[1]
Treasury Stock Value, Excluding Preferred Shares			0	[1]
Total shareholders’ equity			20,059	[1]
Goodwill and other intangible assets, net of associated deferred tax liabilities			(7,341)	[1],[2]
Other adjustments, common tier calculation			0	[1]
Tier one common risk-based capital			12,718	[1]
Preferred stock			0	[1]
Trust preferred capital securities subject to phase-out from tier 1 capital			0	[1]
Other adjustments, tier 1 risk based calculation			0	[1]
Tier One Risk Based Capital			12,718	[1]
Total Capital Qualifying Subordinated Long-Term Debt			1,936	[1]
Other adjustments, total capital calculation			45	[1]
Capital			14,699	[1]
Risk-weighted assets - credit risk			76,197	[1]
Risk-weighted assets - market risk			1,262	[1]
Total risk-weighted assets			77,459	[1]
Adjusted Quarterly Average Assets			199,301	[1]
Tier 1 common risk-based capital			16.40%	[1]
Tier 1 risk-based capital			16.40%	[1]
Total risk-based capital			19.00%	[1]
Tier 1 leverage			6.40%	[1]
State Street Bank | Basel III Advanced Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	10,840	[5]
Retained earnings	9,500	[5]
Accumulated other comprehensive income (loss)	(220)	[5]
Treasury Stock Value, Excluding Preferred Shares	0	[1]
Total shareholders’ equity	20,120	[5]
Goodwill and other intangible assets, net of associated deferred tax liabilities	(5,672)	[2],[5]
Other adjustments, common tier calculation	(132)	[5]
Tier one common risk-based capital	14,316	[5]
Preferred stock	0	[5]
Trust preferred capital securities subject to phase-out from tier 1 capital	0	[5]
Other adjustments, tier 1 risk based calculation	0	[5]
Tier One Risk Based Capital	14,316	[5]
Total Capital Qualifying Subordinated Long-Term Debt	1,754	[1]
Trust preferred capital securities phased out of tier 1 capital	0	[5]
Other adjustments, total capital calculation	0	[5]
Capital	16,070	[5]
Risk-weighted assets - credit risk	60,610	[5]
Risk-weighted assets - operational risk	35,530	[5]
Risk-weighted assets - market risk	3,707	[5]
Total risk-weighted assets	99,847	[5]
Adjusted Quarterly Average Assets	236,340	[5]
Tier 1 common risk-based capital	14.30%	[5]
Tier 1 risk-based capital	14.30%	[5]
Total risk-based capital	16.10%	[5]
Tier 1 leverage	6.10%	[5]
State Street Bank | Basel III Transitional Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	10,840	[6]
Retained earnings	9,500	[6]
Accumulated other comprehensive income (loss)	(220)	[6]
Treasury Stock Value, Excluding Preferred Shares	0	[1]
Total shareholders’ equity	20,120	[6]
Goodwill and other intangible assets, net of associated deferred tax liabilities	(5,672)	[2],[6]
Other adjustments, common tier calculation	(132)	[6]
Tier one common risk-based capital	14,316	[6]
Preferred stock	0	[6]
Trust preferred capital securities subject to phase-out from tier 1 capital	0	[6]
Other adjustments, tier 1 risk based calculation	0	[6]
Tier One Risk Based Capital	14,316	[6]
Total Capital Qualifying Subordinated Long-Term Debt	1,754	[1]
Trust preferred capital securities phased out of tier 1 capital	0	[6]
Other adjustments, total capital calculation	0	[6]
Capital	16,070	[6]
Risk-weighted assets - credit risk	87,150	[6]
Risk-weighted assets - market risk	1,423	[6]
Total risk-weighted assets	88,573	[6]
Adjusted Quarterly Average Assets	$ 236,340	[6]
Tier 1 common risk-based capital	16.20%	[6]
Tier 1 risk-based capital	16.20%	[6]
Total risk-based capital	18.10%	[6]
Tier 1 leverage	6.10%	[6]

[1] Tier 1 common capital, tier 1 capital, total capital and tier 1 leverage ratios as of December 31, 2013 were calculated in conformity with the provisions of Basel I.

[2] Amounts for State Street and State Street Bank as of September 30, 2014 consisted of goodwill, net of associated deferred tax liabilities, and 20% of other intangible assets, net of associated deferred tax liabilities, the latter phased in as a deduction from capital, in conformity with the Basel III final rule.

[3] Minimum requirements will be phased in up to full implementation beginning on January 1, 2019; minimum requirements listed are as of September 30, 2014.

[4] Minimum requirements listed, governed by Basel I, are as of December 31, 2013.

[5] Tier 1 common capital, tier 1 capital and total capital ratios as of September 30, 2014 were calculated in conformity with the advanced approaches provisions of the Basel III final rule. Tier 1 leverage ratio as of September 30, 2014 was calculated in conformity with the Basel III final rule.

[6] Tier 1 common capital, tier 1 capital, total capital and tier 1 leverage ratios as of September 30, 2014 were calculated in conformity with the transitional provisions of the Basel III final rule. Specifically, these ratios reflect tier 1 common, tier 1 and total capital (the numerator) calculated in conformity with the provisions of the Basel III final rule, and total risk-weighted assets or, with respect to the tier 1 leverage ratio, quarterly average assets (in both cases, the denominator), calculated in conformity with the provisions of Basel I.