Noninterest Income - Client Investment Fees (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 222,440	$ 217,257
Sweep money market fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23,049	26,544
Asset management fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9,137	6,671
Repurchase agreement fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11,207	11,267
Client investment fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 43,393	$ 44,482

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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration