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