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Derivatives (Derivatives Associated With Interest Rate Risk Management Activities) (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Customer Interest Rate Contracts |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | $ 2,026,753 | $ 1,697,992
Assets | 22,097 | 39,495
Liabilities | 18,323 | 14,996
Offsetting Upstream Interest Rate Contracts |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 2,026,753 | 1,697,992
Assets | 17,931 | 14,996
Liabilities | 20,720 | 39,495
Customer Interest Rate Contracts Hedging | Hedging Instruments And Hedged Items | Customer Interest Rate Contracts |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 1,608,912 | 1,357,920
Assets | 11,644 | 17,566
Liabilities | 19,780 | 14,277
Customer Interest Rate Contracts Hedging | Hedging Instruments And Hedged Items | Offsetting Upstream Interest Rate Contracts |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 1,608,912 | 1,357,920
Assets | 18,473 | 14,277
Liabilities | 11,019 | 18,066
Debt Hedging | Hedging Instruments And Hedged Items | Interest Rate Swap |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 900,000 | 900,000
Assets | 371 | 1,628
Liabilities |  | 7,276
Debt Hedging | Hedging Instruments And Hedged Items | Term Borrowings |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Term borrowings | $ 900,000 | $ 900,000

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Amount of the hedged item as of the balance sheet date related to the derivative. For example, the hedged balance on a debt instrument. + References No definition available. + Details
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- Definition 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. + References No definition available. + Details
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- Definition Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611 + Details
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- Definition Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611 + Details
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