Loans and Leases Held for Investment and Credit Quality - Summary of Asset Quality Indicators by Portfolio Class and Origination Year (Parenthetical) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 5,142,004	$ 4,881,665
Loans receivable, fair value	600,571	645,201
Loans Insured or Guaranteed by US Government Authorities
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,000,000	2,070,000
Loans Insured or Guaranteed by US Government Authorities | Risk Grades 1 - 4
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,800,000	1,880,000
Loans Insured or Guaranteed by US Government Authorities | Risk Grade 5
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	137,300	134,200
Loans Insured or Guaranteed by US Government Authorities | Risk Grades 6 - 8
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 61,000	$ 63,000