LHFI and Allowance for Loan Losses, LHFI - Aging Analysis of Past Due Loans and Nonaccrual Loans, Excluding Covered Loans by Loan Type (Details) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		$ 12,894	$ 14,323
Nonaccrual		70,694	55,312
Current Loans		7,184,434	7,021,750
Total LHFI		7,268,022	7,091,385
Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		9,518	9,743
Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		2,765	2,280
Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[1]	611	2,300
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		390	214
Nonaccrual		6,308	6,123
Current Loans		690,802	818,386
Total LHFI		697,500	824,723
Construction, Land Development and Other Land [Member] | Past Due 30 to 59 Days [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		336	214
Construction, Land Development and Other Land [Member] | Past Due 90 Days or More [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[1]	54
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		8,023	10,061
Nonaccrual		23,660	23,079
Current Loans		1,608,332	1,616,361
Total LHFI		1,640,015	1,649,501
Secured by 1-4 Family Residential Properties [Member] | Past Due 30 to 59 Days [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		5,468	6,203
Secured by 1-4 Family Residential Properties [Member] | Past Due 60 to 89 Days [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		2,152	1,800
Secured by 1-4 Family Residential Properties [Member] | Past Due 90 Days or More [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[1]	403	2,058
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		163	525
Nonaccrual		22,141	17,800
Current Loans		1,870,936	1,718,151
Total LHFI		1,893,240	1,736,476
Secured by Nonfarm, Nonresidential Properties [Member] | Past Due 30 to 59 Days [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		163	437
Secured by Nonfarm, Nonresidential Properties [Member] | Past Due 60 to 89 Days [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due			88
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		706
Nonaccrual		93	145
Current Loans		272,953	211,083
Total LHFI		273,752	211,228
Other Real Estate Secured [Member] | Past Due 30 to 59 Days [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		448
Other Real Estate Secured [Member] | Past Due 60 to 89 Days [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		258
Commercial and Industrial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,688	966
Nonaccrual		17,827	7,622
Current Loans		1,348,949	1,334,623
Total LHFI		1,368,464	1,343,211
Commercial and Industrial Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,594	921
Commercial and Industrial Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		94	45
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,486	2,424
Nonaccrual		86	31
Current Loans		162,972	166,680
Total LHFI		164,544	169,135
Consumer Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,071	1,835
Consumer Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		261	347
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[1]	154	242
State and Other Political Subdivision Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due			65
Current Loans		787,049	734,550
Total LHFI		787,049	734,615
State and Other Political Subdivision Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due			65
Other Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		438	68
Nonaccrual		579	512
Current Loans		442,441	421,916
Total LHFI		443,458	422,496
Other Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		$ 438	$ 68

[1] Past due 90 days or more but still accruing interest.