EARNINGS PER SHARE (Details) (USD $) In Thousands, except 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
Basic and Diluted Earnings:
Net Income – 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
Basic weighted-average shares outstanding:									17,872,000	18,193,000	18,137,000
Add: Stock options									38,000	12,000	9,000
Diluted weighted-average shares outstanding									17,910,000	18,205,000	18,146,000
Basic Earnings Per 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
Diluted Earnings Per Share:
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
Antidilutive securities from non-qualified stock options excluded from calculating earnings
Number of antidilutive options									4,000	14,000	14,000