BUSINESS COMBINATIONS - Schedule of Assets And Liabilities Acquired (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 01, 2019	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Liabilities
Goodwill		$ 928,005	$ 931,637	$ 911,488
Fidelity Southern Corporation
Assets
Cash and due from banks		23,847
Federal funds sold and interest-bearing deposits in banks		217,936
Investment securities		297,897
Other investments		7,449
Loans held for sale		327,617
Loans	$ 3,510,000	3,512,262
Less allowance for loan losses		0
Loans, net		3,512,262
Other real estate owned		7,178
Premises and equipment		101,249
Other intangible assets, net		50,610
Cash value of bank owned life insurance		72,328
Deferred income taxes, net		0
Other assets		141,723
Total assets		4,760,096
Liabilities
Noninterest-bearing		1,299,715
Interest-bearing		2,741,494
Total deposits		4,041,209
Securities sold under agreements to repurchase		22,345
Other borrowings		151,332
Subordinated deferrable interest debentures		36,718
Deferred tax liability, net		1,318
Other liabilities		64,726
Total liabilities		4,317,648
Net identifiable assets acquired over (under) liabilities assumed		442,448
Goodwill	$ 426,900	426,865
Net assets acquired over liabilities assumed		$ 869,313
Ameris Bancorp common shares issued (in shares)	22,181,522
Price per share of the Company's common stock (in dollars per share)	$ 39.19
Company common stock issued	$ 869,294
Cash exchanged for shares	19
Fair value of total consideration transferred	869,313
Fidelity Southern Corporation | Initial Fair Value Adjustments
Assets
Cash and due from banks	0
Federal funds sold and interest-bearing deposits in banks	0
Investment securities	(1,444)
Other investments	0
Loans held for sale	(1,290)
Loans	(79,002)
Less allowance for loan losses	31,245
Loans, net	(47,757)
Other real estate owned	(427)
Premises and equipment	11,407
Other intangible assets, net	39,940
Cash value of bank owned life insurance	0
Deferred income taxes, net	(104)
Other assets	998
Total assets	1,323
Liabilities
Noninterest-bearing	0
Interest-bearing	942
Total deposits	942
Securities sold under agreements to repurchase	0
Other borrowings	2,265
Subordinated deferrable interest debentures	(9,675)
Deferred tax liability, net	(11,401)
Other liabilities	538
Total liabilities	(17,331)
Net identifiable assets acquired over (under) liabilities assumed	18,654
Goodwill	410,348
Net assets acquired over liabilities assumed	429,002
Fidelity Southern Corporation | Subsequent Adjustments
Assets
Cash and due from banks	(2,417)
Federal funds sold and interest-bearing deposits in banks	0
Investment securities	0
Other investments	0
Loans held for sale	250
Loans	3,852
Less allowance for loan losses	0
Loans, net	3,852
Other real estate owned	0
Premises and equipment	(3,820)
Other intangible assets, net	0
Cash value of bank owned life insurance	0
Deferred income taxes, net	0
Other assets	(17,138)
Total assets	(19,273)
Liabilities
Noninterest-bearing	(2,114)
Interest-bearing	0
Total deposits	(2,114)
Securities sold under agreements to repurchase	0
Other borrowings	(300)
Subordinated deferrable interest debentures	0
Deferred tax liability, net	497
Other liabilities	(839)
Total liabilities	(2,756)
Net identifiable assets acquired over (under) liabilities assumed	(16,517)
Goodwill	16,517
Net assets acquired over liabilities assumed	0
Fidelity Southern Corporation | Previously Reported
Assets
Cash and due from banks	26,264
Federal funds sold and interest-bearing deposits in banks	217,936
Investment securities	299,341
Other investments	7,449
Loans held for sale	328,657
Loans	3,587,412
Less allowance for loan losses	(31,245)
Loans, net	3,556,167
Other real estate owned	7,605
Premises and equipment	93,662
Other intangible assets, net	10,670
Cash value of bank owned life insurance	72,328
Deferred income taxes, net	104
Other assets	157,863
Total assets	4,778,046
Liabilities
Noninterest-bearing	1,301,829
Interest-bearing	2,740,552
Total deposits	4,042,381
Securities sold under agreements to repurchase	22,345
Other borrowings	149,367
Subordinated deferrable interest debentures	46,393
Deferred tax liability, net	12,222
Other liabilities	65,027
Total liabilities	4,337,735
Net identifiable assets acquired over (under) liabilities assumed	440,311
Goodwill	0
Net assets acquired over liabilities assumed	$ 440,311