Loans and Allowance for Credit Losses - Total Loans Outstanding by Portfolio Segment and Class of Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	$ 10,089,117	$ 8,279,778
Unearned discount and fees	(35,194)	(26,351)
Total (Net of unearned discount and fees)	10,053,923	8,253,427
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	6,197,342	5,133,786
Commercial and Industrial \| General C&I
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	3,275,362	2,746,454
Commercial and Industrial \| Energy Sector
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	1,285,775	935,371
Commercial and Industrial \| Restaurant Industry
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	1,096,366	1,035,538
Commercial and Industrial \| Healthcare
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	539,839	416,423
Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	1,330,739	1,158,401
Commercial Real Estate \| Income Producing
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	1,266,791	1,082,929
Commercial Real Estate \| Land and Development
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	63,948	75,472
Consumer
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	2,294,753	1,765,736
Consumer \| Residential Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	2,227,653	1,690,814
Consumer \| Other
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	67,100	74,922
Small Business Lending
Accounts Notes And Loans Receivable [Line Items]
Total loan outstanding and financing receivable	$ 266,283	$ 221,855

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for 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 20
-Section 50
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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.

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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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