Loans (Details Textuals) $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 20,931,460		$ 20,054,716
Allowance for loan losses	276,551		278,335	$ 274,264
Financing Receivable, Modifications, Post-Modification Recorded Investment	17,476	$ 9,038
Restructured Loans Subsequently Accruing	6,000
Ytd Restructured Loans Still On Nonaccrual	$ 11,000
Oil and Gas Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of contracts	56
Loans	$ 577,000		668,000
Allowance for loan losses	$ 30,000		$ 38,000	$ 42,000
Percent of loans	5.20%

Number of financing receivables.

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- Definition

Percent of Loans

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- Definition

Restructured Loans Subsequently Accruing

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Ytd Restructured Loans Still On Nonaccrual

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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