Loans and Leases Held for Investment and Credit Quality - Age Analysis of Past Due Loans and Leases (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans and leases receivable	$ 2,639,840	$ 1,850,480
Total not accruing & past due	101,080	78,712
Current	2,538,760	1,771,768
Greater Than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total not accruing & past due	39,075	40,886
Loans Insured or Guaranteed by US Government Authorities
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans and leases receivable	700,600	305,400
Current	649,800	263,000
Loans Insured or Guaranteed by US Government Authorities | Greater Than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total not accruing & past due	30,100	33,400
Loans Insured or Guaranteed by US Government Authorities | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total not accruing & past due	$ 20,700	$ 9,000