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Derivative Financial Instruments (Schedule of Notional Amounts and Estimated Fair Values of Interest Rate Derivative Contracts Outstanding) (Detail) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Assets [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Notional Amount | $ 13,679 | $ 41,818
Estimated Fair Value | 242 | 368
Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Liabilities [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Notional Amount | 11,147 | 18,812
Estimated Fair Value | (593) | (1,278)
Not Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Assets [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Notional Amount | 430,449 | 206,745
Estimated Fair Value | 1,418 | 2,649
Not Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Swaps Liabilities [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Notional Amount | 541,496 | 694,965
Estimated Fair Value | (12,820) | (25,466)
Not Designated as Hedging Instrument [Member] | Financial Institution Counterparties Loan Lease Interest Rate Caps Assets [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Notional Amount | 114,619 | 85,966
Estimated Fair Value | 480 | 575
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Swaps Assets [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Notional Amount | 541,496 | 694,965
Estimated Fair Value | 17,882 | 25,467
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Swaps Liabilities [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Notional Amount | 430,449 | 206,745
Estimated Fair Value | (4,861) | (2,649)
Not Designated as Hedging Instrument [Member] | Customer Counterparties Loan Lease Interest Rate Caps Liabilities [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Notional Amount | 114,619 | 85,966
Estimated Fair Value | $ (480) | $ (575)

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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 Fair value of the assets less the liabilities of a derivative or group of derivatives. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 3: 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 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13495-108611 + Details
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