Mergers and Acquisitions - Narrative (Details)					1 Months Ended	3 Months Ended		11 Months Ended	12 Months Ended
	May 01, 2019 USD ($) bank_branch	Feb. 01, 2018 USD ($)	Nov. 01, 2017 USD ($) bank_branch $ / shares shares	Jul. 31, 2017 USD ($) bank_branch shares	Jan. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Goodwill								$ 307,112,000	$ 327,425,000	$ 307,112,000	$ 220,591,000
Goodwill adjustment										(858,000)
Merger-related and other charges									6,907,000	5,414,000	13,901,000
FMBT
Business Acquisition [Line Items]
Number of banking offices | bank_branch	4
Assets acquired	$ 244,624,000
Liabilities assumed	212,844,000
Cash payments for acquisition	52,093,000
Goodwill	20,313,000
Goodwill expected to be tax deductible	0
Intangible assets acquired	2,800,000
Premises and equipment, net	8,524,000
FMBT | Merger-related costs
Business Acquisition [Line Items]
Merger-related and other charges									$ 2,020,000.00
FMBT | Core deposit intangible
Business Acquisition [Line Items]
Intangible assets acquired	$ 2,800,000
Expected useful life of intangible assets (in years)	9 years 3 months
Navitas
Business Acquisition [Line Items]
Assets acquired		$ 393,300,000
Liabilities assumed		350,433,000
Consideration transferred		130,246,000
Cash payments for acquisition		84,500,000
Common stock issued as consideration		45,746,000
Goodwill		87,379,000
Goodwill expected to be tax deductible		0
Provisional value adjustment decrease to acquired loans								526,000
Goodwill adjustment								$ 390,000
Value of loans acquired separate from the business combination					$ 19,900,000
Premises and equipment, net		$ 324,000
Navitas | Merger-related costs
Business Acquisition [Line Items]
Merger-related and other charges										$ 4,980,000
FOFN
Business Acquisition [Line Items]
Number of banking offices | bank_branch			14
Assets acquired			$ 730,491,000
Liabilities assumed			657,566,000
Consideration transferred			126,467,000
Cash payments for acquisition			12,802,000
Common stock issued as consideration			113,665,000
Goodwill			53,542,000
Goodwill expected to be tax deductible			0
Intangible assets acquired			$ 8,738,000
Goodwill adjustment							$ (1,160,000)
Number of shares received for each share outstanding (in shares) | shares			0.6178
Cash per common share outstanding (in dollars per share) | $ / shares			$ 1.90
Loans held for sale			$ 10,686,000				10,700,000
Servicing assets							65,000
Provisional value adjustment increase to loans held for sale							2,590,000
Provisional value adjustment decrease to servicing assets							354,000
Premises and equipment, net			12,398,000
Provisional value adjustment for deferred tax asset							$ (1,080,000.00)
FOFN | Subordinated debentures
Business Acquisition [Line Items]
Liabilities assumed			11,500,000
FOFN | Trust preferred securities
Business Acquisition [Line Items]
Liabilities assumed			12,400,000
FOFN | Core deposit intangible
Business Acquisition [Line Items]
Intangible assets acquired			$ 7,830,000
Expected useful life of intangible assets (in years)			11 years 6 months
FOFN | Noncompete agreement
Business Acquisition [Line Items]
Intangible assets acquired			$ 908,000
Expected useful life of intangible assets (in years)			1 year
HCSB
Business Acquisition [Line Items]
Number of banking offices | bank_branch				8
Assets acquired				$ 389,436,000
Liabilities assumed				346,646,000
Consideration transferred				65,831,000
Cash payments for acquisition				31,000
Common stock issued as consideration				65,800,000
Goodwill				24,166,000
Goodwill expected to be tax deductible				0
Intangible assets acquired				$ 5,716,000
Goodwill adjustment						$ 303,000
Number of shares received for each share outstanding (in shares) | shares				0.0050
Premises and equipment, net				$ 7,424,000		7,420,000
Provisional value adjustment decrease to premises and equipment						493,000
Provisional value adjustment for deferred tax asset						$ 190,000
HCSB | Core deposit intangible
Business Acquisition [Line Items]
Intangible assets acquired				$ 3,480,000
Expected useful life of intangible assets (in years)				6 years
HCSB | Noncompete agreement
Business Acquisition [Line Items]
Intangible assets acquired				$ 2,240,000
HCSB | Noncompete agreement | Minimum
Business Acquisition [Line Items]
Expected useful life of intangible assets (in years)				1 year
HCSB | Noncompete agreement | Maximum
Business Acquisition [Line Items]
Expected useful life of intangible assets (in years)				2 years
FOFN and HCSB | Merger-related costs
Business Acquisition [Line Items]
Merger-related and other charges											$ 8,710,000