INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended			36 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Allocation of income taxes [Abstract]
Income tax expense (benefit)	$ 63,716	$ 59,248	$ 50,652
Shareholders' equity for other comprehensive income	(5,655)	1,145	(8,481)
Shareholders' equity for stock option plans	(1,484)	(1,079)	(1,856)
Total	56,577	59,314	40,315
Current [Abstract]
Federal	46,836	62,369	51,014
State	6,359	8,235	7,201
Deferred [Abstract]
Federal	9,361	(10,391)	(6,870)
State	1,160	(965)	(693)
Income Tax Expense (Benefit), Total	63,716	59,248	50,652
Statutory federal income tax rate (in hundredths)				35.00%
Income tax reconciliation [Abstract]
Reversal of deferred tax asset	400	1,600
Tax expense at statutory rates	68,755	65,359	58,591
Increase (decrease) in taxes resulting from [Abstract]
State income taxes, net of federal tax benefit	4,875	4,709	4,230
Tax-exempt interest revenue	(6,269)	(6,881)	(7,371)
Tax-exempt earnings on life insurance	(2,655)	(2,589)	(3,076)
Deductible dividends paid on 401(k) plan	(737)	(617)	(458)
Penalties	1,065	1
Tax credits	(1,999)	(1,871)	(1,771)
Meals and Entertainment	469	481	486
Other, net	212	656	21
Income Tax Expense (Benefit), Total	63,716	59,248	50,652
Deferred tax assets [Abstract]
Loans, principally due to allowance for credit losses	46,721	47,825		$ 46,721
Other real estate owned	989	3,069		989
Mark to market - securities	4,153	4,160		4,153
Accrued liabilities, principally due to compensation arrangements and vacation accruals	15,149	24,153		15,149
Other	84	106		84
Unrecognized pension expense	35,407	34,654		35,407
Total gross deferred tax assets	102,503	113,967		102,503
Less: valuation allowance
Deferred tax assets	102,503	113,967		102,503
Deferred tax liabilities [Abstract]
Lease transactions	14,302	18,868		14,302
Employment benefits	1,382	736		1,382
Premises and equipment, principally due to differences in depreciation	17,418	19,294		17,418
Mortgage servicing rights	24,638	21,652		24,638
Intangible assets	11,972	11,310		11,972
Investments, principally due to interest income recognition	1,974	2,387		1,974
Deferred loan points	6,065	4,785		6,065
Other assets, principally due to expense recognition	9	9		9
Unrealized net losses on available-for-sale securities	3,861	8,764		3,861
Total gross deferred tax liabilities	81,621	87,805		81,621
Net deferred tax liabilities	20,882	26,162		$ 20,882
Stock Options [Member]
Allocation of income taxes [Abstract]
Income tax expense (benefit)	1,500	1,100
Deferred [Abstract]
Income Tax Expense (Benefit), Total	1,500	1,100
Increase (decrease) in taxes resulting from [Abstract]
Income Tax Expense (Benefit), Total	1,500	1,100
BancorpSouth, Inc. (Parent Company Only) [Member]
Allocation of income taxes [Abstract]
Income tax expense (benefit)	(3,051)	(2,818)	(2,420)
Deferred [Abstract]
Income Tax Expense (Benefit), Total	(3,051)	(2,818)	(2,420)
Increase (decrease) in taxes resulting from [Abstract]
Income Tax Expense (Benefit), Total	$ (3,051)	$ (2,818)	$ (2,420)