Noninterest Income - Client Investment Fees (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,056,842	$ 880,951	$ 511,656
Sweep money market fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	74,176	104,236	75,654
Asset management fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	42,768	28,665	23,882
Repurchase agreement fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	15,256	49,167	30,824
Client investment fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 132,200	$ 182,068	$ 130,360