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Allowance for Loan Losses - Recorded Investment in Consumer Loan Classes by Performing and Nonperforming Status (Detail) - USD ($) $ in Thousands | Jun. 30, 2015 | Dec. 31, 2014
--- | --- | ---
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 1,159,198 | $ 976,224
Percentage of Total | 100.00% | 100.00%
Performing Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 1,154,983 | $ 971,798
Percentage of Total | 99.60% | 99.50%
Nonperforming Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 4,215 | $ 4,426
Percentage of Total | 0.40% | 0.50%
Residential Mortgage [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 599,502 | $ 489,586
Percentage of Total | 100.00% | 100.00%
Residential Mortgage [Member] | Performing Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 597,492 | $ 487,250
Percentage of Total | 99.70% | 99.50%
Residential Mortgage [Member] | Nonperforming Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 2,010 | $ 2,336
Percentage of Total | 0.30% | 0.50%
Home Equity [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 457,813 | $ 418,563
Percentage of Total | 100.00% | 100.00%
Home Equity [Member] | Performing Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 455,787 | $ 416,504
Percentage of Total | 99.60% | 99.50%
Home Equity [Member] | Nonperforming Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 2,026 | $ 2,059
Percentage of Total | 0.40% | 0.50%
Consumer Borrower [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 94,437 | $ 65,567
Percentage of Total | 100.00% | 100.00%
Consumer Borrower [Member] | Performing Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 94,258 | $ 65,536
Percentage of Total | 99.80% | 99.90%
Consumer Borrower [Member] | Nonperforming Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 179 | $ 31
Percentage of Total | 0.20% | 0.10%
Consumer Construction [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 7,446 | $ 2,508
Percentage of Total | 100.00% | 100.00%
Consumer Construction [Member] | Performing Financing Receivable [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Recorded investment in consumer loan | $ 7,446 | $ 2,508
Percentage of Total | 100.00% | 100.00%

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- Definition Reflects the aggregate gross carrying amount of all consumer loans and leases held in portfolio, prior to deducting deferred income and the allowance for losses on consumer loans and leases. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5074-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5066-111524 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522 + Details
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