Loans and Leases Held for Investment at Amortized Cost, Net of Allowance for Loan and Lease Losses - Schedule of Components of Portfolio Segment by Class of Financing Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	$ 5,237,277		$ 5,033,154
Allowance for loan and lease losses	(350,495)	$ (355,163)	(327,852)	$ (303,201)	$ (243,260)	$ (144,389)
Loans and leases held for investment, net	4,886,782		4,705,302
Loans pledged as collateral under the FRB discount window	$ 4,000,000		$ 283,600
Allowance Ratios	6.70%		6.50%
Assets pledged as collateral
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net	$ 511,200		$ 156,200
Consumer Portfolio Segment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	4,535,363		4,260,608
Allowance for loan and lease losses	(336,288)	(341,161)	(312,489)	(288,138)	(228,184)	(128,812)
Loans and leases held for investment, net	$ 4,199,075		$ 3,948,119
Allowance Ratios	7.40%		7.30%
Consumer Portfolio Segment | Unsecured personal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	$ 4,094,748		$ 3,866,373
Consumer Portfolio Segment | Residential mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	186,510		199,601
Consumer Portfolio Segment | Secured consumer
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	254,105		194,634
Commercial Portfolio Segment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	701,914		772,546
Allowance for loan and lease losses	(14,207)	$ (14,002)	(15,363)	$ (15,063)	$ (15,076)	$ (15,577)
Loans and leases held for investment, net	$ 687,707		$ 757,183
Allowance Ratios	2.00%		2.00%
Commercial Portfolio Segment | Equipment finance
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	$ 125,289		$ 160,319
Commercial Portfolio Segment | Commercial real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	373,246		373,501
Commercial Portfolio Segment | Commercial and industrial
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	203,379		238,726
Commercial Portfolio Segment | Commercial and industrial loan, PPP
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment	$ 7,600		$ 67,000