Revenue - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 28, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Receivable from clients balance	$ 3,456	$ 3,300
Receivable from mutual funds, insurance companies and other balance	538	540
Revenue from Contracts with Customers [Member]
Disaggregation Of Revenue [Line Items]
Receivable from clients balance	400	346
Receivable from mutual funds, insurance companies and other balance	$ 268	$ 279
Account and Activity Fee Revenue [Member] \| Other Account and Activity Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue recognized period	one-year

Amount due from mutual funds, insurance companies and other for fees and charges arising from transactions related to the entity's brokerage activities and operations.

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount due from customers for fees and charges arising from transactions related to the entity's brokerage activities and operations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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- Definition

Description of timing for satisfying performance obligation in contract with customer. Includes, but is not limited to, as services are rendered, and upon shipment, delivery or completion of service.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130554-203045

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