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Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Detail) - USD ($) $ in Thousands | Jun. 30, 2015 | Dec. 31, 2014
--- | --- | ---
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 3,639,300 | $ 2,892,522
Total percentage of recorded investment in commercial loan | 100.00% | 100.00%
Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 3,436,177 | $ 2,780,315
Total percentage of recorded investment in commercial loan | 94.40% | 96.10%
Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 119,855 | $ 65,968
Total percentage of recorded investment in commercial loan | 3.30% | 2.30%
Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 83,268 | $ 46,239
Total percentage of recorded investment in commercial loan | 2.30% | 1.60%
Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 2,054,935 | $ 1,682,236
Total percentage of recorded investment in commercial loan | 100.00% | 100.00%
Commercial Real Estate [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 1,976,311 | $ 1,635,132
Total percentage of recorded investment in commercial loan | 96.20% | 97.20%
Commercial Real Estate [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 33,328 | $ 23,597
Total percentage of recorded investment in commercial loan | 1.60% | 1.40%
Commercial Real Estate [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 45,296 | $ 23,507
Total percentage of recorded investment in commercial loan | 2.20% | 1.40%
Commercial and Industrial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 1,239,382 | $ 994,138
Total percentage of recorded investment in commercial loan | 100.00% | 100.00%
Commercial and Industrial [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 1,158,898 | $ 948,663
Total percentage of recorded investment in commercial loan | 93.50% | 95.40%
Commercial and Industrial [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 60,251 | $ 30,357
Total percentage of recorded investment in commercial loan | 4.90% | 3.10%
Commercial and Industrial [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 20,233 | $ 15,118
Total percentage of recorded investment in commercial loan | 1.60% | 1.50%
Construction Loans [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 344,983 | $ 216,148
Total percentage of recorded investment in commercial loan | 100.00% | 100.00%
Construction Loans [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 300,968 | $ 196,520
Total percentage of recorded investment in commercial loan | 87.30% | 90.90%
Construction Loans [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 26,276 | $ 12,014
Total percentage of recorded investment in commercial loan | 7.60% | 5.60%
Construction Loans [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 17,739 | $ 7,614
Total percentage of recorded investment in commercial loan | 5.10% | 3.50%

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- Definition Reflects the aggregate gross carrying amount of all commercial loans and leases held in portfolio, prior to deducting deferred income and the allowance for losses on commercial 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 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522 Reference 3: 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 + Details
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