Loans Acquired - Age Analysis of Past Due Acquired Loans, Excluding Loans Covered by Loss Share (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total Loans	$ 13,127,013	$ 11,723,171
Loans Acquired
Financing Receivable, Past Due [Line Items]
Total Past Due	43,001	28,076
Current	3,821,515	3,264,707
Total Loans	3,864,516	3,292,783
90 Days Past Due & Accruing	2	2
Loans Acquired | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	16,487	14,827
Loans Acquired | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	26,514	13,249
Loans Acquired | Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	296	386
Current	9,408	15,272
Total Loans	9,704	15,658
90 Days Past Due & Accruing	0	2
Loans Acquired | Consumer | Other consumer | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	254	337
Loans Acquired | Consumer | Other consumer | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	42	49
Loans Acquired | Real Estate
Financing Receivable, Past Due [Line Items]
Total Past Due	35,046	16,810
Current	3,407,106	2,827,662
Total Loans	3,442,152	2,844,472
90 Days Past Due & Accruing	2	0
Loans Acquired | Real Estate | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	15,895	13,157
Loans Acquired | Real Estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	19,151	3,653
Loans Acquired | Real Estate | Construction
Financing Receivable, Past Due [Line Items]
Total Past Due	8,111	8,310
Current	418,371	421,295
Total Loans	426,482	429,605
90 Days Past Due & Accruing	0	0
Loans Acquired | Real Estate | Construction | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	4	8,283
Loans Acquired | Real Estate | Construction | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	8,107	27
Loans Acquired | Real Estate | Single family residential
Financing Receivable, Past Due [Line Items]
Total Past Due	7,812	7,755
Current	546,722	558,433
Total Loans	554,534	566,188
90 Days Past Due & Accruing	2	0
Loans Acquired | Real Estate | Single family residential | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5,265	4,706
Loans Acquired | Real Estate | Single family residential | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,547	3,049
Loans Acquired | Real Estate | Other commercial
Financing Receivable, Past Due [Line Items]
Total Past Due	19,123	745
Current	2,442,013	1,847,934
Total Loans	2,461,136	1,848,679
90 Days Past Due & Accruing	0	0
Loans Acquired | Real Estate | Other commercial | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	10,626	168
Loans Acquired | Real Estate | Other commercial | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	8,497	577
Loans Acquired | Commercial
Financing Receivable, Past Due [Line Items]
Total Past Due	7,659	10,880
Current	405,001	421,773
Total Loans	412,660	432,653
90 Days Past Due & Accruing	0	0
Loans Acquired | Commercial | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	338	1,333
Loans Acquired | Commercial | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	7,321	9,547
Loans Acquired | Commercial | Commercial
Financing Receivable, Past Due [Line Items]
Total Past Due	7,659	10,844
Current	403,918	420,070
Total Loans	411,577	430,914
90 Days Past Due & Accruing	0	0
Loans Acquired | Commercial | Commercial | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	338	1,302
Loans Acquired | Commercial | Commercial | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	7,321	9,542
Loans Acquired | Commercial | Agricultural
Financing Receivable, Past Due [Line Items]
Total Past Due	0	36
Current	1,083	1,703
Total Loans	1,083	1,739
90 Days Past Due & Accruing	0	0
Loans Acquired | Commercial | Agricultural | Gross 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	31
Loans Acquired | Commercial | Agricultural | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due		$ 5