Regulatory Capital (Details) (USD $) In Millions, unless otherwise specified	Jun. 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	14,114		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%
Tier 1 common risk-based capital			15.50%	[1]
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	5.50%		4.00%
Tier 1 risk-based capital			17.30%	[1]
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%		8.00%
Total risk-based capital			19.70%	[1]
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%		4.00%
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	10,269	[3]
Retained earnings	14,114	[3]
Accumulated other comprehensive income (loss)	328	[3]
Treasury Stock Value, Excluding Preferred Shares	4,405	[1]
Total shareholders’ equity	20,306	[3]
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,100)	[2],[3]
Other adjustments, common tier calculation	(41)	[3]
Tier one common risk-based capital	14,165	[3]
Preferred stock	1,233	[3]
Trust preferred capital securities subject to phase-out from tier 1 capital	475	[3]
Other adjustments, tier 1 risk based calculation	(165)	[3]
Tier One Risk Based Capital	15,708	[3]
Total Capital Qualifying Subordinated Long-Term Debt	1,738	[1]
Trust preferred capital securities phased out of tier 1 capital	475	[3]
Other adjustments, total capital calculation	3	[3]
Capital	17,924	[3]
Risk-weighted assets - credit risk	71,093	[3]
Risk-weighted assets - operational risk	35,985	[3]
Risk-weighted assets - market risk	3,937	[3]
Total risk-weighted assets	111,015	[3]
Adjusted Quarterly Average Assets	227,815	[3]
Tier 1 common risk-based capital	12.80%	[3]
Tier 1 risk-based capital	14.10%	[3]
Total risk-based capital	16.10%	[3]
Tier 1 leverage	6.90%	[3]
Basel III Transitional Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	10,269	[4]
Retained earnings	14,114	[4]
Accumulated other comprehensive income (loss)	328	[4]
Treasury Stock Value, Excluding Preferred Shares	4,405	[1]
Total shareholders’ equity	20,306	[4]
Goodwill and other intangible assets, net of associated deferred tax liabilities	(6,100)	[2],[4]
Other adjustments, common tier calculation	(41)	[4]
Tier one common risk-based capital	14,165	[4]
Preferred stock	1,233	[4]
Trust preferred capital securities subject to phase-out from tier 1 capital	475	[4]
Other adjustments, tier 1 risk based calculation	(165)	[4]
Tier One Risk Based Capital	15,708	[4]
Total Capital Qualifying Subordinated Long-Term Debt	1,738	[1]
Trust preferred capital securities phased out of tier 1 capital	475	[4]
Other adjustments, total capital calculation	3	[4]
Capital	17,924	[4]
Risk-weighted assets - credit risk	86,928	[4]
Risk-weighted assets - market risk	1,679	[4]
Total risk-weighted assets	88,607	[4]
Adjusted Quarterly Average Assets	227,815	[4]
Tier 1 common risk-based capital	16.00%	[4]
Tier 1 risk-based capital	17.70%	[4]
Total risk-based capital	20.20%	[4]
Tier 1 leverage	6.90%	[4]
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	10,832	[3]
Retained earnings	9,579	[3]
Accumulated other comprehensive income (loss)	299	[3]
Treasury Stock Value, Excluding Preferred Shares	0	[1]
Total shareholders’ equity	20,710	[3]
Goodwill and other intangible assets, net of associated deferred tax liabilities	(5,816)	[2],[3]
Other adjustments, common tier calculation	(126)	[3]
Tier one common risk-based capital	14,768	[3]
Preferred stock	0	[3]
Trust preferred capital securities subject to phase-out from tier 1 capital	0	[3]
Other adjustments, tier 1 risk based calculation	0	[3]
Tier One Risk Based Capital	14,768	[3]
Total Capital Qualifying Subordinated Long-Term Debt	1,754	[1]
Trust preferred capital securities phased out of tier 1 capital	0	[3]
Other adjustments, total capital calculation	0	[3]
Capital	16,522	[3]
Risk-weighted assets - credit risk	64,617	[3]
Risk-weighted assets - operational risk	35,566	[3]
Risk-weighted assets - market risk	3,463	[3]
Total risk-weighted assets	103,646	[3]
Adjusted Quarterly Average Assets	224,050	[3]
Tier 1 common risk-based capital	14.20%	[3]
Tier 1 risk-based capital	14.20%	[3]
Total risk-based capital	15.90%	[3]
Tier 1 leverage	6.60%	[3]
State Street Bank | Basel III Transitional Approach
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock and related surplus	10,832	[4]
Retained earnings	9,579	[4]
Accumulated other comprehensive income (loss)	299	[4]
Treasury Stock Value, Excluding Preferred Shares	0	[1]
Total shareholders’ equity	20,710	[4]
Goodwill and other intangible assets, net of associated deferred tax liabilities	(5,816)	[2],[4]
Other adjustments, common tier calculation	(126)	[4]
Tier one common risk-based capital	14,768	[4]
Preferred stock	0	[4]
Trust preferred capital securities subject to phase-out from tier 1 capital	0	[4]
Other adjustments, tier 1 risk based calculation	0	[4]
Tier One Risk Based Capital	14,768	[4]
Total Capital Qualifying Subordinated Long-Term Debt	1,754	[1]
Trust preferred capital securities phased out of tier 1 capital	0	[4]
Other adjustments, total capital calculation	0	[4]
Capital	16,522	[4]
Risk-weighted assets - credit risk	83,524	[4]
Risk-weighted assets - market risk	1,679	[4]
Total risk-weighted assets	85,203	[4]
Adjusted Quarterly Average Assets	$ 224,050	[4]
Tier 1 common risk-based capital	17.30%	[4]
Tier 1 risk-based capital	17.30%	[4]
Total risk-based capital	19.40%	[4]
Tier 1 leverage	6.60%	[4]

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

[4] Tier 1 common capital, tier 1 capital, total capital and tier 1 leverage ratios as of June 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.