Loans (Narrative) (Details) $ in Thousands, loan in Millions	12 Months Ended
Dec. 31, 2017 USD ($) contract	Dec. 31, 2016 USD ($) loan contract	Dec. 31, 2015 USD ($) contract
Financing Receivable, Recorded Investment [Line Items]
Loans to related parties	$ 10,000	$ 10,100
Loans and Leases Receivable, Related Parties, Additions	203
Repayments on related party loans	350
Financing Receivable, Recorded Investment, Nonaccrual Status	66,189
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	2,400	$ 1,900	$ 1,300
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing, Number of Loans	581
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	$ 293
Financing Receivable Modifications Additional Commitment To Lend	$ 506	$ 508
Financing Receivable, Modifications, Subsequent Default, Number of Contracts \| contract	0	0	0
Loans Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans pledged to collateralize Federal Home Loan Bank Advances	$ 2,250,000	$ 2,290,000
Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans pledged to collateralize Federal Reserve Bank Borrowings	$ 70,200	$ 54,200

Financing Receivable Modifications Additional Commitment To Lend

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Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing, Number of Loans

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Loans and Leases Receivable, Nonaccrual of Interest, Commitments of Additional Funds

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Loans pledged to collateralize Federal Home Loan Bank Advances

+ References

No definition available.

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Loans pledged to collateralize Federal Reserve Bank Borrowings

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No definition available.

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524

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Recorded investment in financing receivables that are 90 days or more past due and still accruing.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18794-111554

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For an unclassified balance sheet, reflects the carrying amount of unpaid loan amounts due from related parties at the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(e))
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Reflects the amount of new advances made to related parties in the form of loan and lease receivables.

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Amount of cash inflow from related parties which reduce the amount of loans and leases receivable due from related parties.

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