Loans (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) contract	Sep. 30, 2019 USD ($) contract	Sep. 30, 2020 USD ($) contract	Sep. 30, 2019 USD ($) contract	Dec. 31, 2019 USD ($)
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Interest Receivable, loans	$ 56,718		$ 56,718		$ 46,839
Financing Receivable Modifications Additional Commitment To Lend	$ 641		$ 641		1,100
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | contract	0	0	0	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default		$ 26		$ 26
Loan modifications, short-term deferments not classified as TDR, Number of contracts | contract			103
Loan modifications, short-term deferments not classified as TDR, net of unearned income			$ 114,400
Paycheck Protection Program (PPP) loans, net of unearned income	$ 953,200		953,200
Loans Receivable [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	3,490,000		3,490,000		3,240,000
Commercial Loan [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Loans pledged to collateralize Federal Reserve Bank Borrowings	200,600		200,600		151,300
Loans [Member]
Financing Receivable, Credit Quality Indicator - interest written off on nonaccrual loans [Line Items]
Interest Receivable, loans	$ 43,400		$ 43,400		$ 33,000