Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Loan Portfolio [Abstract]
Total LHFI	$ 6,447,073	$ 6,449,469
Less allowance for loan losses, LHFI	71,166	69,616
Net LHFI	6,375,907	6,379,853
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	68,438	79,343
LHFI, Collectively Evaluated For Impairment	6,378,635	6,370,126
Total LHFI	6,447,073	6,449,469
Construction, Land Development And Other Land Properties [Member] \| Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	682,444	619,877
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	10,888	13,867
LHFI, Collectively Evaluated For Impairment	671,556	606,010
Total LHFI	682,444	619,877
Secured by 1-4 Family Residential Properties [Member] \| Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	1,637,933	1,634,397
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	24,882	25,621
LHFI, Collectively Evaluated For Impairment	1,613,051	1,608,776
Total LHFI	1,637,933	1,634,397
Secured by Nonfarm, Nonresidential Properties [Member] \| Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	1,567,035	1,553,193
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	19,030	25,717
LHFI, Collectively Evaluated For Impairment	1,548,005	1,527,476
Total LHFI	1,567,035	1,553,193
Other Real Estate Secured [Member] \| Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	240,056	253,787
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	610	1,318
LHFI, Collectively Evaluated For Impairment	239,446	252,469
Total LHFI	240,056	253,787
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,219,684	1,270,350
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	12,411	12,104
LHFI, Collectively Evaluated For Impairment	1,207,273	1,258,246
Total LHFI	1,219,684	1,270,350
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	165,215	167,964
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	44	88
LHFI, Collectively Evaluated For Impairment	165,171	167,876
Total LHFI	165,215	167,964
State and Other Political Subdivision Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	574,265	602,727
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	0	0
LHFI, Collectively Evaluated For Impairment	574,265	602,727
Total LHFI	574,265	602,727
Other Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	360,441	347,174
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	573	628
LHFI, Collectively Evaluated For Impairment	359,868	346,546
Total LHFI	$ 360,441	$ 347,174

The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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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.

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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 after allowance and 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 and loans held for sale.

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