Loans - Narrative (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($) loan	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Purchased with Credit Deterioration, Discount (Premium)	$ 20,600
Loans and Leases Receivable, Deferred Income	4,100
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	2,800,000			$ 2,500,000
Financing Receivable, Paycheck Protection Program	408,900			709,900
Financing Receivable, Paycheck Protection Program, Net of Deferred Fees	396,700
Financing Receivable, Paycheck Protection Program, Unearned Fees	12,200
financing receivable, paycheck protection program, net of deferred fees				698,600
financing recievable, paycheck protection program, unearned fees				11,300
Financing Receivable, Amount Still in Deferral Status	8,500
net premium, acquired loans				16,100
Nonperforming loan balances, excluding government guaranteed balances				3,900
Other Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable	24,600
Non-Covered Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Post-Modification Outstanding Recorded Balance		$ 3,886
Financing Receivable, Modifications, Number of Contracts | loan		3
Restructured, accruing	3,042			3,559
Loans, before unearned loan fees	7,241,500			7,241,074
Financing receivable, allowance for credit loss	128,185	$ 110,270	$ 131,527	136,671	$ 92,187	$ 69,995	$ 43,288
Nonperforming loan balances, excluding government guaranteed balances	3,900
Non-Covered Loans | Enterprise Value Lending Portfolio Niche Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	20,100
Non-Covered Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured, accruing	0			0
Loans, before unearned loan fees	235,431			187,083
Financing receivable, allowance for credit loss	6,958	$ 1,729	$ 3,400	$ 2,787	$ 1,547	$ 1,050	$ 1,134
Non-Covered Loans | Agriculture Portfolio Niche Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	19,000
Cumulative Effect, Period Of Adoption, Adjustment | Non-Covered Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	$ 12,900