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Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Details) - Commercial - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 4,503,594 | $ 4,355,395
% of Total | 100.00% | 100.00%
Pass |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 4,302,762 | $ 4,169,721
% of Total | 95.50% | 95.70%
Special mention |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 130,101 | $ 88,198
% of Total | 2.90% | 2.00%
Substandard |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 70,731 | $ 97,476
% of Total | 1.60% | 2.30%
Commercial real estate |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 2,685,994 | $ 2,498,476
% of Total | 100.00% | 100.00%
Commercial real estate | Pass |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 2,588,847 | $ 2,423,742
% of Total | 96.40% | 97.00%
Commercial real estate | Special mention |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 66,436 | $ 33,098
% of Total | 2.50% | 1.30%
Commercial real estate | Substandard |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 30,711 | $ 41,636
% of Total | 1.10% | 1.70%
Commercial and industrial |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 1,433,266 | $ 1,401,035
% of Total | 100.00% | 100.00%
Commercial and industrial | Pass |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 1,345,810 | $ 1,315,507
% of Total | 93.90% | 93.90%
Commercial and industrial | Special mention |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 54,320 | $ 40,409
% of Total | 3.80% | 2.90%
Commercial and industrial | Substandard |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 33,136 | $ 45,119
% of Total | 2.30% | 3.20%
Commercial construction |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 384,334 | $ 455,884
% of Total | 100.00% | 100.00%
Commercial construction | Pass |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 368,105 | $ 430,472
% of Total | 95.80% | 94.40%
Commercial construction | Special mention |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 9,345 | $ 14,691
% of Total | 2.40% | 3.20%
Commercial construction | Substandard |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Loans recorded investment | $ 6,884 | $ 10,721
% of Total | 1.80% | 2.40%

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- Definition Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: 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=82891408&loc=d3e4428-111522 + Details
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