Loans and Allowance for Loan Losses - Table of loan payment estimates (Details) - USD ($) $ in Thousands			12 Months Ended
	Nov. 30, 2017	Jan. 03, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans			$ (5,064)	$ (4,604)	$ (4,627)	$ (3,395)
Contractual principal and interest	$ 113,584		452,818	626,691
Non-accretable difference	(27,248)		(13,938)	(24,818)
Cash flows expected to be collected	86,336		438,880	601,873
Accretable Yield			(82,098)	(116,754)
Accretable difference	(7,369)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance	78,967		361,846	489,723	623,430
Acquired loans, net			356,782	485,119	618,803
Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			1,760,427	2,594,826
After fair value adjustment			1,800
Acquired non-credit impaired loans accounted under FASB 310 20 | Park Sterling Corporation
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest	2,200,000
After fair value adjustment	2,100,000
Fair value adjustment	$ 46,500,000
Acquired non-credit impaired loans accounted under FASB 310 20 | Southeastern Bank Financial
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest		$ 78,963
Non-accretable difference		(13,072)
Cash flows expected to be collected		65,891
Accretable difference		(4,910)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance		60,981
Acquired credit impaired loans accounted under FASB 310 30
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans			(5,064)	(4,604)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			361,846	489,723
Acquired loans, net			356,782	485,119
Acquired loans accounted under FASB ASC 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest			1,800,000	2,600,000
After fair value adjustment				2,600,000
Fair value adjustment			20,300	33,400
Acquired credit impaired and non-impaired loans accounted under FASB ASC Topic 310-20 | Southeastern Bank Financial
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest		1,000,000
After fair value adjustment		986,500
Fair value adjustment		$ 18,800
Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			1,760,427	2,594,826
Residential real estate
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			163,359	207,482
Residential real estate | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans			(2,555)	(2,246)	(3,553)	(2,419)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			163,359	207,482	260,787
Residential real estate | Acquired credit impaired loans accounted under FASB 310 30
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			163,359	207,482
Commercial non-owner occupied real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			481,010	844,323
Commercial owner occupied real estate loan | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
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
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			307,193	421,841
Consumer loans | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans			(539)	(761)	(461)	(558)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			35,488	42,492	51,453
Consumer loans | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			685,163	871,238
Consumer loans | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			774,647	983,015
Commercial and industrial
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			7,029	10,043
Commercial and industrial | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans			(24)	(79)	(145)	(238)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			7,029	10,043	26,946
Commercial and industrial | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			101,880	212,537
Commercial and industrial | Acquired credit impaired loans accounted under FASB 310 30
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			7,029	10,043
Commercial and industrial | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			101,880	212,537
Other income producing property | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
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
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			95,697	133,110
Consumer
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			35,488	42,492
Consumer | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			35,488	42,492
Consumer | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			89,484	111,777
Consumer | Acquired credit impaired loans accounted under FASB 310 30
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			35,488	42,492
Consumer | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			89,484	111,777
Commercial loans | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			985,780	1,611,811
Construction and land development | Commercial non-owner occupied real estate | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans			(569)	(717)	(180)	(139)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			25,032	32,942	49,649
Construction and land development | Commercial non-owner occupied real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			33,569	165,070
Construction and land development | Commercial non-owner occupied real estate | Acquired credit impaired loans accounted under FASB 310 30
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			25,032	32,942
Construction and land development | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			33,569	165,070
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans			(1,377)	(801)	(288)	$ (41)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			130,938	196,764	$ 234,595
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			447,441	679,253
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired credit impaired loans accounted under FASB 310 30
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			130,938	196,764
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			447,441	679,253
Home equity loans | Consumer loans | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			188,732	242,425
Home equity loans | Consumer loans | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			188,732	242,425
Other Consumer | Consumer loans | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			89,484	111,777
Consumer Owner Occupied Loans | Consumer loans | Acquired non-credit impaired loans accounted under FASB 310 20
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			496,431	628,813
Consumer Owner Occupied Loans | Consumer loans | Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance			$ 496,431	$ 628,813