Quarterly report pursuant to Section 13 or 15(d)

SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details)

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SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2014
Dec. 31, 2013
Mar. 31, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Amortized Cost $ 1,067,142 $ 675,474  
Gross Unrealized Gains 18,822 11,701  
Gross Unrealized (Losses) (7,265) (9,827)  
Total securities available for sale, Estimated Fair Value 1,078,699 677,348 583,217
US Government Agencies Debt Securities [Member]
      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Amortized Cost 1,552 1,654  
Gross Unrealized Gains 1,622 499  
Gross Unrealized (Losses)        
Total securities available for sale, Estimated Fair Value 3,174 2,153  
Obligations of States and Political Subdivisions [Member]
      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Amortized Cost 427,388 255,335  
Gross Unrealized Gains 10,346 6,107  
Gross Unrealized (Losses) (4,083) (6,612)  
Total securities available for sale, Estimated Fair Value 433,651 254,830  
Corporate and Other Bonds [Member]
      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Amortized Cost 72,881 9,479  
Gross Unrealized Gains 262 115  
Gross Unrealized (Losses) (521) (160)  
Total securities available for sale, Estimated Fair Value 72,622 9,434  
Mortgage Backed Securities [Member]
      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Amortized Cost 552,000 405,389  
Gross Unrealized Gains 6,564 4,954  
Gross Unrealized (Losses) (2,601) (2,981)  
Total securities available for sale, Estimated Fair Value 555,963 407,362  
Other Securities [Member]
      
Schedule of Trading Securities and Other Trading Assets [Line Items]      
Amortized Cost 13,321 3,617  
Gross Unrealized Gains 28 26  
Gross Unrealized (Losses) (60) (74)  
Total securities available for sale, Estimated Fair Value $ 13,289 $ 3,569