QUARTERLY FINANCIAL INFORMATION OF REGISTRANT (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 33,015	$ 30,811	$ 29,215	$ 26,561	$ 26,398	$ 28,464	$ 29,442	$ 31,716	$ 119,602	$ 116,020	$ 131,038
Interest expense	4,353	4,170	4,344	5,101	5,822	6,456	6,897	7,720	17,968	26,895	35,631
Net interest income	28,662	26,641	24,871	21,460	20,576	22,008	22,545	23,996	101,634	89,125	95,407
Provision for loan losses	2,726	3,640	2,021	492	2,245	3,265	2,174	3,052	8,879	10,736	7,496
(Loss) gain on sale of securities available for sale	(732)	(142)	5,001	4,345	4,395	4,302	3,297	5,972	8,472	17,966	11,795
(Loss) gain on sale of securities carried at fair value through income	0	0	0	0	0	0	(13)	(485)	0	(498)	937
FHLB advance option impairment charges	0	0	0	0	0	(195)	(1,364)	(472)	0	(2,031)	(8,923)
Noninterest income excluding net securities gains (losses) and FHLB advance option impairment	8,228	6,555	6,095	5,895	6,259	6,391	6,142	5,792	35,245	40,021	35,322
Noninterest expense	19,964	20,264	21,166	20,319	19,413	19,076	19,096	18,522	81,713	76,107	72,348
Income before income tax expense	13,468	9,150	12,780	10,889	9,572	10,165	9,337	13,229	46,287	42,303	50,885
Provision for income tax expense	1,281	257	1,712	1,847	1,352	1,558	1,608	3,090	5,097	7,608	10,394
Net income attributable to Southside Bancshares, Inc.	$ 12,187	$ 8,893	$ 11,068	$ 9,042	$ 8,220	$ 8,607	$ 7,729	$ 10,139	$ 41,190	$ 34,695	$ 39,133
Earnings per common share
Earnings per common share - basic (in dollars per share)	$ 0.68	$ 0.50	$ 0.62	$ 0.51	$ 0.45	$ 0.47	$ 0.42	$ 0.56	$ 2.30	$ 1.91	$ 2.16
Earnings per common share - diluted (in dollars per share)	$ 0.68	$ 0.50	$ 0.62	$ 0.51	$ 0.45	$ 0.47	$ 0.42	$ 0.56	$ 2.30	$ 1.91	$ 2.16