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Derivatives and Hedging Activities (Derivative Financial Instruments included in OCI and Current Earnings) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent |  | $ 443 | $ 2,170 | $ 1,199
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Borrowings Expense, before Tax | [1] | (441) | (2,520) | (2,828)
Derivatives designated as hedges: [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net |  |  | (2,520) | (2,828)
Derivatives not designated as hedges: [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Other income |  | (54) | (44) | (43)
Other Expense [Member] | Derivatives not designated as hedges: [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Other income |  | (21) | (82) | (53)
Other Income [Member] | Derivatives not designated as hedges: [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Other income |  | 6 | 73 | 60
Mortgage banking income | Derivatives not designated as hedges: [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Increase Decrease In Fair Value Of Unhedged Derivative Instruments Relating To Residential Loans |  | (39) | (35) | (50)
Derivatives designated as hedges: [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent |  | $ 443 | $ 2,170 | $ 1,199
[1] | Includes the amortization of the remaining balance of a realized but unrecognized gain, net of tax, from the termination of interest rate swaps in 2009. The original gain of $1.4 million, net of tax, will be recognized in earnings through December 2018, the original maturity date of the swap. The balance of this gain had amortized to $137,000, $281,000, and $427,000 at December 31, 2017, 2016, and 2015, respectively.

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- Definition The increase (decrease) during the period, which was recognized in earnings, in the unrealized gains or losses on derivative instruments relating to residential loans that are not or are no longer designated as hedging instruments. + References No definition available. + Details
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- Definition Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Borrowings Expense, before Tax + References No definition available. + Details
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- Definition The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4D -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959 + Details
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- Definition Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 + Details
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- Definition Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss), attributable to parent entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569643-111683 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=84161450&loc=SL4573702-111684 + Details
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