Acquisitions - Pro Forma Financial Information (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net revenues	$ 291,254
Net income from continuing operations applicable to Piper Sandler Companies	$ 11,482

Amount after tax of pro forma income from continuing operations as if the business combination had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration