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Basis of Presentation - Stock Dividend Percentage (Details)
 3 Months Ended 0 Months Ended
Mar. 31, 2015
Rate
Apr. 13, 2015
Subsequent Event [Line Items]    
Stock dividend, declared Apr. 13, 2015  
Stock dividend declared, percentage of common stock 5.00%sbsi_StockDividendsPercentageOfCommonStock  
Stock dividend declared    
Subsequent Event [Line Items]    
Stock dividend, declared   Apr. 13, 2015
Stock dividend declared, percentage of common stock   5.00%sbsi_StockDividendsPercentageOfCommonStock
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= us-gaap_DividendDeclaredMember
Stock Dividends Payable, Date of Record   Apr. 27, 2015
Stock Dividends Payable, Date to be Paid   May 14, 2015