Loans (Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and Industrial	$ 4,344,000	$ 4,120,522
Energy	1,386,061	1,758,195
Commercial mortgages	3,481,157	3,285,041
Construction	1,043,261	720,695
Land	311,030	286,991
Total commercial real estate	4,835,448	4,292,727
Home equity loans	345,130	340,528
Home equity lines of credit	264,862	233,525
Other	326,793	306,696
Total consumer real estate	936,785	880,749
Total real estate	5,772,233	5,173,476
Consumer and Other	473,098	434,338
Total loans	11,975,392	11,486,531
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Energy	971,767	1,249,678
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Energy	221,213	272,934
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Energy	$ 193,081	$ 235,583

Loans and Leases Receivable Consumer Home Equity Lines Of Credit

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- Definition

Loans And Leases Receivable Real Estate

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Loans Receivable, Gross, Energy

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Amount before allowance of revolving, open-end loan, extended under a line of credit and secured by the borrower's residential property. 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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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Amount before allowance of other consumer installment 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.

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Amount before allowance of consumer loans and leases not otherwise specified in the taxonomy. 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.

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Amount before allowance of consumer real estate loans. Includes, but not limited to, construction financing, residential mortgage loans, and home equity lines of credit. 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

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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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Amount before allowance of loans issued to commercial and industrial institutions. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes real estate loans and loans covered under loss sharing agreements.

+ References

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Amount before allowance of commercial construction loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount before allowance of commercial loans to develop land for sale or construction thereon. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount before allowance of mortgage loans on existing land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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