Goodwill and intangible assets - Narrative (Details)	3 Months Ended	9 Months Ended
Jun. 30, 2021 USD ($)	Sep. 30, 2021 Segment reporting_unit
Goodwill [Line Items]
Number of reportable segments (segment) \| Segment		3
Number of reporting units (reporting unit) \| reporting_unit		6
Goodwill impairment \| $	$ 0
Investment Services
Goodwill [Line Items]
Number of reporting units (reporting unit) \| Segment		4
Investment and Wealth Management
Goodwill [Line Items]
Number of reporting units (reporting unit) \| reporting_unit		2

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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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

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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8672-108599

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Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

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