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Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Details) - Commercial - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 4,491,982	$ 4,503,594
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 4,223,695	$ 4,302,762
Total percentage of recorded investment in commercial loan	94.00%	95.50%
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 148,680	$ 130,101
Total percentage of recorded investment in commercial loan	3.30%	2.90%
Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 119,607	$ 70,731
Total percentage of recorded investment in commercial loan	2.70%	1.60%
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 2,760,891	$ 2,685,994
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 2,625,232	$ 2,588,847
Total percentage of recorded investment in commercial loan	95.10%	96.40%
Commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 68,204	$ 66,436
Total percentage of recorded investment in commercial loan	2.50%	2.50%
Commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 67,455	$ 30,711
Total percentage of recorded investment in commercial loan	2.40%	1.10%
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 1,406,950	$ 1,433,266
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 1,294,478	$ 1,345,810
Total percentage of recorded investment in commercial loan	92.00%	93.90%
Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 65,557	$ 54,320
Total percentage of recorded investment in commercial loan	4.70%	3.80%
Commercial and industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 46,915	$ 33,136
Total percentage of recorded investment in commercial loan	3.30%	2.30%
Commercial construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 324,141	$ 384,334
Total percentage of recorded investment in commercial loan	99.99%	100.00%
Commercial construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 303,985	$ 368,105
Total percentage of recorded investment in commercial loan	93.80%	95.80%
Commercial construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 14,919	$ 9,345
Total percentage of recorded investment in commercial loan	4.60%	2.40%
Commercial construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 5,237	$ 6,884
Total percentage of recorded investment in commercial loan	1.60%	1.80%

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Loans and leases receivable gross carrying amount commercial percentage.

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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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