Noninterest Income - Client Investment Fees (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 880,951	$ 511,656
Sweep money market fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	104,236	75,654	$ 28,485
Asset management fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	28,665	23,882	16,831
Repurchase agreement fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	49,167	30,824	10,820
Client investment fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 182,068	$ 130,360	$ 56,136

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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