Loans and Allowance for Loan Losses - Credit risk profile by risk grade of non acquired loans (Details) - USD ($)
$ in Thousands

Dec. 31, 2019

Dec. 31, 2018

Dec. 31, 2017

Nov. 30, 2017

Dec. 31, 2016

Loans and Allowance for Loan Losses

Other Real Estate, Non Covered

$ 11,964

$ 11,410

$ 11,203

$ 18,316

Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

9,252,831

7,933,286

6,492,155

Classified assets

49,500

56,600

Other Real Estate, Non Covered

3,600

3,900

Non-acquired loans | Pass

Loans and Allowance for Loan Losses

Total loans

9,123,097

7,813,938

Non-acquired loans | Special mention

Loans and Allowance for Loan Losses

Total loans

83,830

66,645

Non-acquired loans | Substandard and doubtful

Loans and Allowance for Loan Losses

Total loans

45,900

52,700

Non-acquired loans | Substandard

Loans and Allowance for Loan Losses

Total loans

45,904

52,703

Acquired non-credit impaired loans

Loans and Allowance for Loan Losses

Total loans

1,760,427

2,594,826

3,507,907

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

1,760,427

2,594,826

Acquired non-credit impaired loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

1,697,942

2,523,010

Acquired non-credit impaired loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

39,772

48,716

Acquired non-credit impaired loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

22,713

23,100

Acquired credit impaired loans

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

361,846

489,723

623,430

$ 78,967

Acquired credit impaired loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

218,364

296,106

Acquired credit impaired loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

58,281

74,388

Acquired credit impaired loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

85,201

119,229

Residential real estate

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

163,359

207,482

Residential real estate | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

82,203

104,181

Residential real estate | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

35,968

41,964

Residential real estate | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

45,188

61,337

Residential real estate | Acquired credit impaired loans

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

163,359

207,482

260,787

Commercial non-owner occupied real estate | Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

2,779,498

2,256,996

Commercial non-owner occupied real estate | Non-acquired loans | Construction and land development

Loans and Allowance for Loan Losses

Total loans

968,360

841,445

830,875

Commercial non-owner occupied real estate | Non-acquired loans | Construction and land development | Pass

Loans and Allowance for Loan Losses

Total loans

959,206

832,612

Commercial non-owner occupied real estate | Non-acquired loans | Construction and land development | Special mention

Loans and Allowance for Loan Losses

Total loans

7,095

6,015

Commercial non-owner occupied real estate | Non-acquired loans | Construction and land development | Substandard

Loans and Allowance for Loan Losses

Total loans

2,059

2,818

Commercial non-owner occupied real estate | Non-acquired loans | Other commercial non-owner occupied real estate

Loans and Allowance for Loan Losses

Total loans

1,811,138

1,415,551

1,008,893

Commercial non-owner occupied real estate | Non-acquired loans | Other commercial non-owner occupied real estate | Pass

Loans and Allowance for Loan Losses

Total loans

1,787,306

1,407,744

Commercial non-owner occupied real estate | Non-acquired loans | Other commercial non-owner occupied real estate | Special mention

Loans and Allowance for Loan Losses

Total loans

22,410

6,427

Commercial non-owner occupied real estate | Non-acquired loans | Other commercial non-owner occupied real estate | Substandard

Loans and Allowance for Loan Losses

Total loans

1,422

1,380

Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

33,569

165,070

Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

31,690

163,777

Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

966

838

Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

913

455

Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate

Loans and Allowance for Loan Losses

Total loans

447,441

679,253

817,166

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

447,441

679,253

Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

432,710

665,913

Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

14,162

13,018

Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

569

322

Commercial non-owner occupied real estate | Acquired credit impaired loans | Construction and land development

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

25,032

32,942

49,649

Commercial non-owner occupied real estate | Acquired credit impaired loans | Construction and land development | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

17,756

20,293

Commercial non-owner occupied real estate | Acquired credit impaired loans | Construction and land development | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

2,904

3,001

Commercial non-owner occupied real estate | Acquired credit impaired loans | Construction and land development | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

4,372

9,648

Commercial non-owner occupied real estate | Acquired credit impaired loans | Other commercial non-owner occupied real estate

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

130,938

196,764

234,595

Commercial non-owner occupied real estate | Acquired credit impaired loans | Other commercial non-owner occupied real estate | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

108,762

160,788

Commercial non-owner occupied real estate | Acquired credit impaired loans | Other commercial non-owner occupied real estate | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

6,465

14,393

Commercial non-owner occupied real estate | Acquired credit impaired loans | Other commercial non-owner occupied real estate | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

15,711

21,583

Commercial owner occupied real estate loan | Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

1,784,017

1,517,551

1,262,776

Commercial owner occupied real estate loan | Non-acquired loans | Pass

Loans and Allowance for Loan Losses

Total loans

1,754,801

1,480,267

Commercial owner occupied real estate loan | Non-acquired loans | Special mention

Loans and Allowance for Loan Losses

Total loans

19,742

24,576

Commercial owner occupied real estate loan | Non-acquired loans | Substandard

Loans and Allowance for Loan Losses

Total loans

9,474

12,708

Commercial owner occupied real estate loan | Acquired non-credit impaired loans

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

307,193

421,841

Commercial owner occupied real estate loan | Acquired non-credit impaired loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

300,678

411,783

Commercial owner occupied real estate loan | Acquired non-credit impaired loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

3,092

5,664

Commercial owner occupied real estate loan | Acquired non-credit impaired loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

3,423

4,394

Consumer loans | Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

2,637,467

2,431,413

Consumer loans | Non-acquired loans | Home equity loans

Loans and Allowance for Loan Losses

Total loans

518,628

495,148

437,642

Consumer loans | Non-acquired loans | Home equity loans | Pass

Loans and Allowance for Loan Losses

Total loans

508,054

481,607

Consumer loans | Non-acquired loans | Home equity loans | Special mention

Loans and Allowance for Loan Losses

Total loans

4,490

7,293

Consumer loans | Non-acquired loans | Home equity loans | Substandard

Loans and Allowance for Loan Losses

Total loans

6,084

6,248

Consumer loans | Non-acquired loans | Other Consumer

Loans and Allowance for Loan Losses

Total loans

13,892

9,357

Consumer loans | Non-acquired loans | Other Consumer | Pass

Loans and Allowance for Loan Losses

Total loans

13,892

9,357

Consumer loans | Non-acquired loans | Consumer Owner Occupied Loans

Loans and Allowance for Loan Losses

Total loans

2,118,839

1,936,265

1,530,260

Consumer loans | Non-acquired loans | Consumer Owner Occupied Loans | Pass

Loans and Allowance for Loan Losses

Total loans

2,094,080

1,909,427

Consumer loans | Non-acquired loans | Consumer Owner Occupied Loans | Special mention

Loans and Allowance for Loan Losses

Total loans

9,585

11,304

Consumer loans | Non-acquired loans | Consumer Owner Occupied Loans | Substandard

Loans and Allowance for Loan Losses

Total loans

15,174

15,534

Consumer loans | Acquired non-credit impaired loans

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

774,647

983,015

Consumer loans | Acquired non-credit impaired loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

747,880

953,739

Consumer loans | Acquired non-credit impaired loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

12,767

16,254

Consumer loans | Acquired non-credit impaired loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

14,000

13,022

Consumer loans | Acquired non-credit impaired loans | Home equity loans

Loans and Allowance for Loan Losses

Total loans

188,732

242,425

320,591

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

188,732

242,425

Consumer loans | Acquired non-credit impaired loans | Home equity loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

174,912

227,515

Consumer loans | Acquired non-credit impaired loans | Home equity loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

5,679

7,688

Consumer loans | Acquired non-credit impaired loans | Home equity loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

8,141

7,222

Consumer loans | Acquired non-credit impaired loans | Other Consumer

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

89,484

111,777

Consumer loans | Acquired non-credit impaired loans | Other Consumer | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

86,535

108,833

Consumer loans | Acquired non-credit impaired loans | Other Consumer | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

654

698

Consumer loans | Acquired non-credit impaired loans | Other Consumer | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

2,295

2,246

Consumer loans | Acquired non-credit impaired loans | Consumer Owner Occupied Loans

Loans and Allowance for Loan Losses

Total loans

496,431

628,813

710,611

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

496,431

628,813

Consumer loans | Acquired non-credit impaired loans | Consumer Owner Occupied Loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

486,433

617,391

Consumer loans | Acquired non-credit impaired loans | Consumer Owner Occupied Loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

6,434

7,868

Consumer loans | Acquired non-credit impaired loans | Consumer Owner Occupied Loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

3,564

3,554

Consumer loans | Acquired credit impaired loans

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

35,488

42,492

51,453

Commercial and industrial

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

7,029

10,043

Commercial and industrial | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

5,160

5,093

Commercial and industrial | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

286

546

Commercial and industrial | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

1,583

4,404

Commercial and industrial | Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

1,280,859

1,054,952

815,187

Commercial and industrial | Non-acquired loans | Pass

Loans and Allowance for Loan Losses

Total loans

1,256,465

1,037,915

Commercial and industrial | Non-acquired loans | Special mention

Loans and Allowance for Loan Losses

Total loans

16,055

5,887

Commercial and industrial | Non-acquired loans | Substandard

Loans and Allowance for Loan Losses

Total loans

8,339

11,150

Commercial and industrial | Acquired non-credit impaired loans

Loans and Allowance for Loan Losses

Total loans

101,880

212,537

398,696

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

101,880

212,537

Commercial and industrial | Acquired non-credit impaired loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

97,092

202,399

Commercial and industrial | Acquired non-credit impaired loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

2,948

6,523

Commercial and industrial | Acquired non-credit impaired loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

1,840

3,615

Commercial and industrial | Acquired credit impaired loans

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

7,029

10,043

26,946

Other income producing property | Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

218,617

214,353

193,847

Other income producing property | Non-acquired loans | Pass

Loans and Allowance for Loan Losses

Total loans

213,291

208,186

Other income producing property | Non-acquired loans | Special mention

Loans and Allowance for Loan Losses

Total loans

3,966

4,706

Other income producing property | Non-acquired loans | Substandard

Loans and Allowance for Loan Losses

Total loans

1,360

1,461

Other income producing property | Acquired non-credit impaired loans

Loans and Allowance for Loan Losses

Total loans

95,697

133,110

196,669

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

95,697

133,110

Other income producing property | Acquired non-credit impaired loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

87,892

125,399

Other income producing property | Acquired non-credit impaired loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

5,837

6,419

Other income producing property | Acquired non-credit impaired loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

1,968

1,292

Consumer

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

35,488

42,492

Consumer | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

4,483

5,751

Consumer | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

12,658

14,484

Consumer | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

18,347

22,257

Consumer | Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

538,481

448,664

378,985

Consumer | Non-acquired loans | Pass

Loans and Allowance for Loan Losses

Total loans

536,002

446,823

Consumer | Non-acquired loans | Special mention

Loans and Allowance for Loan Losses

Total loans

487

437

Consumer | Non-acquired loans | Substandard

Loans and Allowance for Loan Losses

Total loans

1,992

1,404

Consumer | Non-acquired loans | All Consumer

Loans and Allowance for Loan Losses

Total loans

3,189,840

2,889,434

Consumer | Non-acquired loans | All Consumer | Pass

Loans and Allowance for Loan Losses

Total loans

3,152,028

2,847,214

Consumer | Non-acquired loans | All Consumer | Special mention

Loans and Allowance for Loan Losses

Total loans

14,562

19,034

Consumer | Non-acquired loans | All Consumer | Substandard

Loans and Allowance for Loan Losses

Total loans

23,250

23,186

Consumer | Acquired non-credit impaired loans

Loans and Allowance for Loan Losses

Total loans

89,484

111,777

137,710

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

89,484

111,777

Consumer | Acquired credit impaired loans

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

35,488

42,492

Commercial loans | Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

6,062,991

5,043,852

Commercial loans | Non-acquired loans | Pass

Loans and Allowance for Loan Losses

Total loans

5,971,069

4,966,724

Commercial loans | Non-acquired loans | Special mention

Loans and Allowance for Loan Losses

Total loans

69,268

47,611

Commercial loans | Non-acquired loans | Substandard

Loans and Allowance for Loan Losses

Total loans

22,654

29,517

Commercial loans | Acquired non-credit impaired loans

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

985,780

1,611,811

Commercial loans | Acquired non-credit impaired loans | Pass

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

950,062

1,569,271

Commercial loans | Acquired non-credit impaired loans | Special mention

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

27,005

32,462

Commercial loans | Acquired non-credit impaired loans | Substandard

Loans and Allowance for Loan Losses

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance

8,713

10,078

Commercial loans | Acquired non-credit impaired loans | Construction and land development

Loans and Allowance for Loan Losses

Total loans

33,569

165,070

403,357

Commercial loans | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate

Loans and Allowance for Loan Losses

Total loans

307,193

421,841

521,818

Other loans

Loans and Allowance for Loan Losses

Total loans

1,289

Other loans | Non-acquired loans

Loans and Allowance for Loan Losses

Total loans

$ 13,892

$ 9,357

$ 33,690