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Business Combinations - Narrative (Details) $ / shares in Units, $ in Thousands |  |  | 2 Months Ended | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Oct. 15, 2020 director $ / shares | Feb. 01, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2020 USD ($) $ / shares | Dec. 31, 2019 USD ($) $ / shares | Dec. 31, 2018 USD ($) | May 01, 2019 USD ($) | Apr. 02, 2019 USD ($) | Nov. 01, 2018 USD ($) | Oct. 02, 2018 USD ($) | May 01, 2018 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of directors of new entity | director | 14 |  |  |  |  |  |  |  |  |  |
Goodwill |  |  |  | $ 350,298 | $ 349,398 | $ 236,347 |  |  |  |  |
Merger-related expenses |  |  |  | $ 17,450 | 17,166 | $ 6,462 |  |  |  |  |
Disposal group, premium for deposits sold, percent |  |  |  | 8.00% |  |  |  |  |  |  |
Deposits |  |  |  | $ 43,431,609 | $ 34,431,236 |  |  |  |  |  |
Class A Common Stock |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares | $ 1.00 |  |  | $ 1 | $ 1 |  |  |  |  |  |
CIT Group Inc. |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares | $ 0.01 |  |  |  |  |  |  |  |  |  |
Number of directors of new entity | director | 3 |  |  |  |  |  |  |  |  |  |
CIT Group Inc. | BancShares Class A Common Stock |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Common stock, conversion ratio | 0.06200 |  |  |  |  |  |  |  |  |  |
CIT Group Inc. | Fixed-To-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series A |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Preferred stock, par value (in dollars per share) | $ / shares | $ 0.01 |  |  |  |  |  |  |  |  |  |
CIT Group Inc. | Non-Cumulative Perpetual Preferred Stock, Series B |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Preferred stock, par value (in dollars per share) | $ / shares | $ 0.01 |  |  |  |  |  |  |  |  |  |
Preferred Stock, dividend rate, percentage | 5.625% |  |  |  |  |  |  |  |  |  |
CIT Group Inc. | Series B Preferred Stock |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Common stock, conversion ratio | 1 |  |  |  |  |  |  |  |  |  |
CIT Group Inc. | Series C Preferred Stock |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Common stock, conversion ratio | 1 |  |  |  |  |  |  |  |  |  |
BancShares |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of directors of new entity | director | 11 |  |  |  |  |  |  |  |  |  |
Community Financial Holding Co. Inc. |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Payments to acquire businesses |  | $ 2,300 |  |  |  |  |  |  |  |  |
Total assets acquired |  | 221,400 |  |  |  |  |  |  |  |  |
Non-PCI loans acquired |  | 110,600 |  |  |  |  |  |  |  |  |
PCI loans acquired |  | 23,400 |  |  |  |  |  |  |  |  |
Business combination, recognized identifiable assets acquired and liabilities assumed, allowance for credit losses |  | 1,200 |  |  |  |  |  |  |  |  |
Intangible assets |  | 536 |  |  |  |  |  |  |  |  |
Total liabilities assumed |  | 219,766 |  |  |  |  |  |  |  |  |
Deposits |  | 209,340 |  |  |  |  |  |  |  |  |
Goodwill |  | $ 686 |  |  |  |  |  |  |  |  |
Merger-related expenses |  |  |  | $ 3,500 |  |  |  |  |  |  |
Interest and fee income, loans, consumer and commercial |  |  | $ 5,300 |  |  |  |  |  |  |  |
Entegra Financial |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total assets acquired |  |  |  | 1,680,000 |  |  |  |  |  |  |
Non-PCI loans acquired |  |  |  |  |  |  |  |  |  |  | $ 953,700
PCI loans acquired |  |  |  |  |  |  |  |  |  |  | $ 77,500
Total liabilities assumed |  |  |  | 1,510,000 |  |  |  |  |  |  |
Deposits |  |  |  | 1,330,000 |  |  |  |  |  |  |
Goodwill |  |  |  | 52,600 |  |  |  |  |  |  |
Business combination, measurement period adjustment, amount |  |  |  | 214 |  |  |  |  |  |  |
Merger-related expenses |  |  |  | 7,800 | $ 5,400 |  |  |  |  |  |
Interest and fee income, loans, consumer and commercial |  |  |  | 40,300 | 0 |  |  |  |  |  |
Core deposit intangible acquired |  |  |  | 4,500 |  |  |  |  |  |  |
Disposal group, including discontinued operation, accounts, notes and loans receivable |  |  |  | 110,100 |  |  |  |  |  |  |
Disposal group, including discontinued operation, property, plant and equipment |  |  |  | 2,100 |  |  |  |  |  |  |
Disposal group, deposits sold |  |  |  | 184,800 |  |  |  |  |  |  |
First South Bancorp |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total assets acquired |  |  |  |  |  |  | $ 239,200 |  |  |  |
Non-PCI loans acquired |  |  |  |  |  |  |  |  |  | $ 162,800 |
PCI loans acquired |  |  |  |  |  |  |  |  |  | $ 16,400 |
Total liabilities assumed |  |  |  | 0 | 1,067 |  | 215,600 |  |  |  |
Deposits |  |  |  |  |  |  | 207,600 |  |  |  |
Goodwill |  |  |  |  |  |  | 13,900 |  |  |  |
Merger-related expenses |  |  |  | 0 | 4,100 |  |  |  |  |  |
Interest and fee income, loans, consumer and commercial |  |  |  | 5,700 | 6,100 |  |  |  |  |  |
Core deposit intangible acquired |  |  |  |  |  |  | $ 2,300 |  |  |  |
Biscayne Bancshares |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total assets acquired |  |  |  |  |  |  |  | $ 1,030,000 |  |  |
Non-PCI loans acquired |  |  |  |  |  |  |  |  | $ 850,400 |  |
PCI loans acquired |  |  |  |  |  |  |  |  | $ 13,000 |  |
Total liabilities assumed |  |  |  | 0 | 1,138 |  |  | 956,800 |  |  |
Goodwill |  |  |  |  |  |  |  | 46,500 |  |  |
Merger-related expenses |  |  |  | 847 | 5,800 |  |  |  |  |  |
Interest and fee income, loans, consumer and commercial |  |  |  | $ 37,800 | $ 33,800 |  |  |  |  |  |
Core deposit intangible acquired |  |  |  |  |  |  |  | 4,700 |  |  |
Deposits |  |  |  |  |  |  |  | $ 786,500 |  |  |

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