Loans and Allowance for Probable Loan Losses - Loans by Credit Quality Indicator (Details) - USD ($) $ in Thousands		Jun. 30, 2015		Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	[1]	$ 2,179,863		$ 2,181,133
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net		20,291		21,346
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		2,118,939		2,118,189
Pass Watch
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		2,219		5,528
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		4,075	[2]	6,713	[3]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	[2]	100		700
Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		41,214	[2]	49,244	[3]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	[2]	4,400		17,800
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		13,416	[2]	1,459
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	[2]	10,400
Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		295,633		267,830
Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		290,038		260,183
Construction | Pass Watch
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		29		862
Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		1,366	[2]	1,394	[3]
Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		4,174	[2]	5,363	[3]
Construction | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		26	[2]	28
1-4 Family Residential
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		683,944		690,895
1-4 Family Residential | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		670,852		677,559
1-4 Family Residential | Pass Watch
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		1,428		1,453
1-4 Family Residential | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		1,664	[2]	1,706	[3]
1-4 Family Residential | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		6,305	[2]	9,167	[3]
1-4 Family Residential | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		3,695	[2]	1,010
Other
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		500,906		468,171
Other | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		489,166		455,394
Other | Pass Watch
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		0		2,416
Other | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		83	[2]	2,569	[3]
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		11,657	[2]	7,792	[3]
Other | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		0	[2]	0
Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		228,789		226,460
Commercial Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		200,583		199,306
Commercial Loans | Pass Watch
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		751		781
Commercial Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		962	[2]	1,044	[3]
Commercial Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		17,910	[2]	25,102	[3]
Commercial Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		8,583	[2]	227
Municipal Loans
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		256,492		257,492
Municipal Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		255,543		256,543
Municipal Loans | Pass Watch
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		0		0
Municipal Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		0	[2]	0	[3]
Municipal Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		699	[2]	949	[3]
Municipal Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		250	[2]	0
Loans to Individuals
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		214,099		270,285
Loans to Individuals | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		212,757		269,204
Loans to Individuals | Pass Watch
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		11		16
Loans to Individuals | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		0	[2]	0	[3]
Loans to Individuals | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		469	[2]	871	[3]
Loans to Individuals | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross		$ 862	[2]	$ 194

[1] Includes approximately $679.7 million and $763.3 million of loans acquired with the Omni acquisition as of June 30, 2015 and December 31, 2014, respectively. These loans were measured at fair value at the acquisition date with no carryover of allowance for loan loss.

[2] Includes $0.1 million special mention, $4.4 million substandard, and $10.4 million doubtful of PCI loans as of June 30, 2015.

[3] Includes $0.7 million special mention and $17.8 million substandard of PCI loans as of December 31, 2014.