Line of Business Information - Summary of Line of Business (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Servicing fees	$ 1,273	$ 1,238
Management fees	301	292
Trading services	324stt_TradingServicesRevenue	253stt_TradingServicesRevenue
Securities finance	101	85
Processing fees and other	61us-gaap_FeesAndCommissionsOther	56us-gaap_FeesAndCommissionsOther
Total fee revenue	2,060us-gaap_FeesAndCommissions	1,924us-gaap_FeesAndCommissions
Net interest revenue	546us-gaap_InterestIncomeExpenseNet	555us-gaap_InterestIncomeExpenseNet
Gains (losses) related to investment securities, net	(1)us-gaap_MarketableSecuritiesGainLoss	6us-gaap_MarketableSecuritiesGainLoss
Total revenue	2,605us-gaap_Revenues	2,485us-gaap_Revenues
Provision for loan losses	4us-gaap_ProvisionForLoanAndLeaseLosses	2us-gaap_ProvisionForLoanAndLeaseLosses
Total expenses	2,097us-gaap_NoninterestExpense	2,028us-gaap_NoninterestExpense
Income before income tax expense	504	455
Pre-tax margin	19.00%stt_PreTaxMargin	18.00%stt_PreTaxMargin
Investment Servicing
Segment Reporting Information [Line Items]
Servicing fees	1,273	1,238
Management fees	0	0
Trading services	315	241
Securities finance	101	85
Processing fees and other	59	55
Total fee revenue	1,748	1,619
Net interest revenue	545	551
Gains (losses) related to investment securities, net	(1)	6
Total revenue	2,292	2,176
Provision for loan losses	4	2
Total expenses	1,836	1,672
Income before income tax expense	452	502
Pre-tax margin	20.00%	23.00%
Investment Management
Segment Reporting Information [Line Items]
Servicing fees	0	0
Management fees	301	292
Trading services	9	12
Securities finance	0	0
Processing fees and other	2	1
Total fee revenue	312	305
Net interest revenue	1	4
Gains (losses) related to investment securities, net	0	0
Total revenue	313	309
Provision for loan losses	0	0
Total expenses	256	245
Income before income tax expense	57	64
Pre-tax margin	18.00%	21.00%
Other
Segment Reporting Information [Line Items]
Servicing fees	0	0
Management fees	0	0
Trading services	0	0
Securities finance	0	0
Processing fees and other	0	0
Total fee revenue	0	0
Net interest revenue	0	0
Gains (losses) related to investment securities, net	0	0
Total revenue	0	0
Provision for loan losses	0	0
Total expenses	5	111
Income before income tax expense	$ (5)	$ (111)

Pre-tax margin

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- Definition

Trading Services Revenue

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No definition available.

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- Definition

Amount of fees and commissions from financial services and banking activities and correspondent clearing. Includes fees from depositor accounts, credit cards, merchant discounts, and fiduciary and trust activities, guarantee fees, investment advisory, management, and administrative fees, transfer agent fees, and insurance commissions.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 13

-Article 9

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Income from services rendered by trust departments or by any consolidated subsidiaries acting in a fiduciary capacity, including fees earned for (1) acting as an agent for fiduciary placement and loans and (2) custody or investment advisory services when such fees are not separately billed to the customer. This item excludes commissions and fees received for the accumulation or disbursement of funds deposited to Individual Retirement or Keogh plan accounts when such are not handled by the reporting entity's trust department.

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-Topic 942

-SubTopic 225

-Section S99

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-Subparagraph (SX 210.9-04.13 (a))

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Fee and commission revenue earned from sources not otherwise specified in the existing taxonomy.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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-Publisher FASB

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-Topic 235

-SubTopic 10

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-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(1)(i))

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- Definition

The net amount of operating interest income (expense).

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-Topic 942

-SubTopic 225

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Amount of revenue from providing investment advisory, asset management and administrative services, including, but not limited to, distribution and shareholder services, accounting, tax, legal, regulatory filing, share registration, and shareholder correspondence activities.

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No definition available.

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Fees and commissions from underwriting securities, private placements of securities, investment advisory and management services, merger and acquisition services, and other related consulting fees. Include fees and commissions from securities brokerage activities, from the sale and servicing of mutual funds, from the purchase and sale of securities and money market instruments where the bank is acting as agent for other banks or customers, and from the lending of securities owned by the bank or by bank customers (exclusive of trading revenue). Also includes the bank's proportionate share of the income or loss before extraordinary items and other adjustments from its investments in: unconsolidated subsidiaries, associated companies and corporate joint ventures, unincorporated joint ventures, general partnerships, and limited partnerships over which the bank exercises significant influence and that are principally engaged in investment banking, advisory, brokerage, or securities underwriting activities.

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-Topic 942

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- Definition

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

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-Subparagraph (SX 210.5-03.7(c))

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-Section 03

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-Subparagraph (a),(c)-(e)

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Total aggregate amount of all noninterest expense.

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Amount of expense related to estimated loss from loan and lease transactions.

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-Topic 230

-SubTopic 10

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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