Loans (Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and Industrial	$ 5,111,957	$ 4,792,388
Energy	1,602,598	1,499,093
Commercial mortgages	4,121,966	3,887,742
Construction	1,267,717	1,066,696
Land	306,755	331,986
Total commercial real estate	5,696,438	5,286,424
Home equity loans	353,924	355,342
Home equity lines of credit	337,168	291,950
Other	427,898	376,002
Total consumer real estate	1,118,990	1,023,294
Total real estate	6,815,428	6,309,718
Consumer and Other	569,750	544,466
Total loans	14,099,733	13,145,665
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Energy	1,309,314	1,182,326
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Energy	168,775	171,795
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Energy	$ 124,509	$ 144,972

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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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.

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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.

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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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