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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

Loans and leases receivable gross carrying amount commercial percentage.

+ References

No definition available.

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+ References

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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

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