Loans and Allowance for Loan Losses - Loans by Credit Risk Rating, Segregated by Class of Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 14,425,260	$ 11,723,171
Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	14,112,831	11,523,787
Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	102,618	80,394
Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	209,421	118,407
Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	173	583
Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	217	0
Loans, Excluding Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	9,630,076	8,430,388
Loans, Excluding Acquired Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	396,748	405,470
Loans, Excluding Acquired Loans | Consumer | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	394,511	402,507
Loans, Excluding Acquired Loans | Consumer | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Consumer | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,237	2,963
Loans, Excluding Acquired Loans | Consumer | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Consumer | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Consumer | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	204,802	204,173
Loans, Excluding Acquired Loans | Consumer | Credit cards | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	204,161	203,667
Loans, Excluding Acquired Loans | Consumer | Credit cards | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Consumer | Credit cards | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	641	506
Loans, Excluding Acquired Loans | Consumer | Credit cards | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Consumer | Credit cards | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Consumer | Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	191,946	201,297
Loans, Excluding Acquired Loans | Consumer | Other consumer | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	190,350	198,840
Loans, Excluding Acquired Loans | Consumer | Other consumer | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Consumer | Other consumer | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,596	2,457
Loans, Excluding Acquired Loans | Consumer | Other consumer | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Consumer | Other consumer | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,884,422	5,966,453
Loans, Excluding Acquired Loans | Real Estate | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,791,168	5,910,329
Loans, Excluding Acquired Loans | Real Estate | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	33,790	20,707
Loans, Excluding Acquired Loans | Real Estate | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	59,461	35,182
Loans, Excluding Acquired Loans | Real Estate | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	3	235
Loans, Excluding Acquired Loans | Real Estate | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Real Estate | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,760,894	1,300,723
Loans, Excluding Acquired Loans | Real Estate | Construction and development | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,754,269	1,296,988
Loans, Excluding Acquired Loans | Real Estate | Construction and development | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	49	1,910
Loans, Excluding Acquired Loans | Real Estate | Construction and development | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,576	1,825
Loans, Excluding Acquired Loans | Real Estate | Construction and development | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Real Estate | Construction and development | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Real Estate | Single family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,444,620	1,440,443
Loans, Excluding Acquired Loans | Real Estate | Single family residential | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,415,603	1,420,052
Loans, Excluding Acquired Loans | Real Estate | Single family residential | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,868	1,628
Loans, Excluding Acquired Loans | Real Estate | Single family residential | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	24,146	18,528
Loans, Excluding Acquired Loans | Real Estate | Single family residential | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	3	235
Loans, Excluding Acquired Loans | Real Estate | Single family residential | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Real Estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	3,678,908	3,225,287
Loans, Excluding Acquired Loans | Real Estate | Other commercial | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	3,621,296	3,193,289
Loans, Excluding Acquired Loans | Real Estate | Other commercial | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	28,873	17,169
Loans, Excluding Acquired Loans | Real Estate | Other commercial | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	28,739	14,829
Loans, Excluding Acquired Loans | Real Estate | Other commercial | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Real Estate | Other commercial | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,073,192	1,939,423
Loans, Excluding Acquired Loans | Commercial | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,998,143	1,904,826
Loans, Excluding Acquired Loans | Commercial | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	25,226	8,432
Loans, Excluding Acquired Loans | Commercial | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	49,823	26,165
Loans, Excluding Acquired Loans | Commercial | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Commercial | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,909,796	1,774,909
Loans, Excluding Acquired Loans | Commercial | Commercial | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,835,335	1,742,002
Loans, Excluding Acquired Loans | Commercial | Commercial | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	25,185	8,357
Loans, Excluding Acquired Loans | Commercial | Commercial | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	49,276	24,550
Loans, Excluding Acquired Loans | Commercial | Commercial | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Commercial | Commercial | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Commercial | Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	163,396	164,514
Loans, Excluding Acquired Loans | Commercial | Agricultural | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	162,808	162,824
Loans, Excluding Acquired Loans | Commercial | Agricultural | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	41	75
Loans, Excluding Acquired Loans | Commercial | Agricultural | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	547	1,615
Loans, Excluding Acquired Loans | Commercial | Agricultural | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Commercial | Agricultural | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	275,714	119,042
Loans, Excluding Acquired Loans | Other | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	275,714	119,042
Loans, Excluding Acquired Loans | Other | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Other | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Other | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans, Excluding Acquired Loans | Other | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,795,184	3,292,783
Loans acquired | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,653,295	3,187,083
Loans acquired | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	43,602	51,255
Loans acquired | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	97,900	54,097
Loans acquired | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	170	348
Loans acquired | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	217	0
Loans acquired | Consumer | Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	57,748	15,658
Loans acquired | Consumer | Other consumer | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	57,318	15,380
Loans acquired | Consumer | Other consumer | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Consumer | Other consumer | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	430	278
Loans acquired | Consumer | Other consumer | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Consumer | Other consumer | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	3,999,658	2,844,472
Loans acquired | Real Estate | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	3,900,116	2,768,761
Loans acquired | Real Estate | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	42,074	38,839
Loans acquired | Real Estate | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	57,304	36,524
Loans acquired | Real Estate | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	127	348
Loans acquired | Real Estate | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	37	0
Loans acquired | Real Estate | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	475,967	429,605
Loans acquired | Real Estate | Construction and development | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	474,750	393,122
Loans acquired | Real Estate | Construction and development | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	21	27,621
Loans acquired | Real Estate | Construction and development | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,159	8,862
Loans acquired | Real Estate | Construction and development | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Real Estate | Construction and development | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	37	0
Loans acquired | Real Estate | Single family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	997,444	566,188
Loans acquired | Real Estate | Single family residential | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	978,681	553,460
Loans acquired | Real Estate | Single family residential | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,181	2,081
Loans acquired | Real Estate | Single family residential | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	17,455	10,299
Loans acquired | Real Estate | Single family residential | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	127	348
Loans acquired | Real Estate | Single family residential | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Real Estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,526,247	1,848,679
Loans acquired | Real Estate | Other commercial | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,446,685	1,822,179
Loans acquired | Real Estate | Other commercial | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	40,872	9,137
Loans acquired | Real Estate | Other commercial | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	38,690	17,363
Loans acquired | Real Estate | Other commercial | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Real Estate | Other commercial | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	737,778	432,653
Loans acquired | Commercial | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	695,861	402,942
Loans acquired | Commercial | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,528	12,416
Loans acquired | Commercial | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	40,166	17,295
Loans acquired | Commercial | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	43	0
Loans acquired | Commercial | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	180	0
Loans acquired | Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	585,720	430,914
Loans acquired | Commercial | Commercial | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	548,928	401,300
Loans acquired | Commercial | Commercial | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,528	12,416
Loans acquired | Commercial | Commercial | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	35,041	17,198
Loans acquired | Commercial | Commercial | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	43	0
Loans acquired | Commercial | Commercial | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	180	0
Loans acquired | Commercial | Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	152,058	1,739
Loans acquired | Commercial | Agricultural | Risk Rate 1-4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	146,933	1,642
Loans acquired | Commercial | Agricultural | Risk Rate 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Commercial | Agricultural | Risk Rate 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,125	97
Loans acquired | Commercial | Agricultural | Risk Rate 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Loans acquired | Commercial | Agricultural | Risk Rate 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 0	$ 0