Loans (Narrative) (Details) $ in Thousands, loan in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) contract	Dec. 31, 2018 USD ($) loan contract	Dec. 31, 2017 USD ($) contract
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Nonaccrual	$ 33,060
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	2,000	$ 3,600	$ 2,400
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing, Number of Loans	0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing, Number of Loans | loan		0.0
Loans and Leases Receivable, Nonaccrual of Interest, Commitments of Additional Funds	2,000	$ 2,100
Financing Receivable Modifications Additional Commitment To Lend	$ 1,100	$ 2,100
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | contract	1	0	0
Loans Receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans pledged to collateralize Federal Home Loan Bank Advances	$ 3,240,000	$ 3,220,000
Commercial Loan [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans pledged to collateralize Federal Reserve Bank Borrowings	$ 151,300	$ 82,000