Loans and Leases - Narrative (Details)	3 Months Ended
	Mar. 31, 2021 USD ($) contract	Mar. 31, 2020 USD ($) contract	Dec. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable, 90 or more days past due	$ 33,423,000		$ 36,523,000
Receivable, 30-89 days past due	17,128,000		12,232,000
Nonaccrual loans and leases	67,652,000	$ 95,602,000	91,163,000
Allowance for Loan and Lease Losses, Period Increase (Decrease)	(55,700,000)
Provision	(53,000,000.0)	98,000,000
Gross loans and leases held for investment	19,055,165,000		19,153,357,000
Loans and Leases Receivable, Allowance	292,445,000	221,292,000	348,181,000	$ 142,402,000	$ 138,785,000
Real Estate Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable, 90 or more days past due	26,885,000		29,518,000
Receivable, 30-89 days past due	6,538,000		7,350,000
Nonaccrual loans and leases	48,907,000	21,396,000	45,557,000
Provision	2,603,000	41,865,000
Gross loans and leases held for investment	7,992,490,000		7,905,193,000
Loans and Leases Receivable, Allowance	141,122,000	91,372,000	138,342,000	49,883,000	44,575,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable, 90 or more days past due	5,834,000		6,894,000
Receivable, 30-89 days past due	8,395,000		2,863,000
Nonaccrual loans and leases	17,471,000	73,442,000	44,902,000
Provision	(45,810,000)	37,459,000
Gross loans and leases held for investment	7,120,049,000		7,534,801,000
Loans and Leases Receivable, Allowance	78,716,000	$ 87,570,000	126,403,000	$ 68,388,000	$ 61,528,000
Residential Real Estate | Real Estate Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable, 90 or more days past due	1,052,000		373,000
Receivable, 30-89 days past due	6,502,000		600,000
Nonaccrual loans and leases	$ 2,471,000		1,826,000
Number of Loans | contract	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	$ 163,000
Finance Receivable, Payroll Protection Program Loan [Member] | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans and leases held for investment	1,100,000,000
Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases	$ 31,400,000
Percentage of nonaccrual loans and leases	46.00%
Nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable, 90 or more days past due	$ 33,400,000		36,500,000
Receivable, 30-89 days past due	600,000		3,400,000
Financing receivable, nonaccrual status, current	$ 33,600,000		51,300,000
Other Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | contract	1	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	$ 87,000	$ 9,000
Other Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable, 90 or more days past due	3,954,000		4,766,000
Receivable, 30-89 days past due	1,645,000		2,323,000
Nonaccrual loans and leases	12,660,000		40,243,000
Venture Capital Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | contract		1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default		$ 2,300,000
Venture Capital Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable, 90 or more days past due	0		0
Receivable, 30-89 days past due	6,750,000		540,000
Nonaccrual loans and leases	$ 2,432,000		$ 1,980,000