Loans and Leases - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) contract	Sep. 30, 2020 USD ($) contract	Sep. 30, 2021 USD ($) contract	Sep. 30, 2020 USD ($) contract	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	$ 64,507,000	$ 85,615,000	$ 64,507,000	$ 85,615,000		$ 91,163,000
Allowance for Loan and Lease Losses, Period Increase (Decrease)			(21,900,000)
Provision	(21,500,000)	81,000,000	(146,500,000)	272,000,000
Gross loans and leases held for investment	20,588,255,000		20,588,255,000			19,153,357,000
Loans and Leases Receivable, Allowance	203,733,000	345,966,000	203,733,000	345,966,000	$ 225,600,000	348,181,000	$ 301,050,000	$ 142,402,000	$ 138,785,000
Real Estate Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	33,162,000	47,128,000	33,162,000	47,128,000		45,557,000
Provision	(11,344,000)	(7,588,000)	(47,466,000)	77,684,000
Gross loans and leases held for investment	9,590,037,000		9,590,037,000			7,905,193,000
Loans and Leases Receivable, Allowance	96,203,000	121,694,000	96,203,000	121,694,000	107,013,000	138,342,000	130,724,000	49,883,000	44,575,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	10,932,000	37,759,000	10,932,000	37,759,000		44,902,000
Provision	(9,792,000)	64,921,000	(77,373,000)	121,804,000
Gross loans and leases held for investment	6,892,846,000		6,892,846,000			7,534,801,000
Loans and Leases Receivable, Allowance	47,497,000	$ 128,265,000	47,497,000	$ 128,265,000	$ 57,697,000	126,403,000	$ 97,947,000	$ 68,388,000	$ 61,528,000
Residential Real Estate [Member] | Real Estate Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	7,547,000		7,547,000			1,826,000
Finance Receivable, Payroll Protection Program Loan [Member] | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans and leases held for investment	279,400,000		279,400,000
Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	16,600,000		$ 16,600,000
Credit Concentration Risk | Nonaccrual Loans And Leases Benchmark | Fair Value, Concentration of Risk, All Financial Instruments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of nonaccrual loans and leases			26.00%
Nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable, 90 or more days past due	30,700,000		$ 30,700,000			36,500,000
Receivable, 30-89 days past due	700,000		700,000			3,400,000
Financing receivable, nonaccrual status, current	$ 33,200,000		$ 33,200,000			51,300,000
Other Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | contract	2		2	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	$ 95,000		$ 95,000	$ 5,000
Other Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	6,979,000		6,979,000			40,243,000
Venture Capital Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	$ 2,348,000		$ 2,348,000			1,980,000
Asset-based
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | contract	1		1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	$ 479,000		$ 479,000
Asset-based | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	$ 1,605,000		$ 1,605,000			$ 2,679,000
Real Estate Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | contract		1		1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default		$ 412,000		$ 412,000