Quarterly report pursuant to Section 13 or 15(d)

SECURITIES (Amortized Cost of AFS Securities by Security Type and Credit Rating) (Details)

v3.20.1
SECURITIES (Amortized Cost of AFS Securities by Security Type and Credit Rating) (Details) - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost $ 1,900,313 $ 1,893,427
Standard & Poor's AAA/AA/A | Moody's AAA/AA/A    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 588,018  
Standard & Poor's BBB/BB/B | Moody's BBB/BB/B    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 23,886  
Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 1,170,237  
Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 118,172  
U.S. government and agency securities    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 17,631 21,149
U.S. government and agency securities | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 2,497  
U.S. government and agency securities | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 0  
U.S. government and agency securities | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 15,134  
U.S. government and agency securities | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 0  
Obligations of states and political subdivisions    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 515,914 421,344
Obligations of states and political subdivisions | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 514,374  
Obligations of states and political subdivisions | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 1,033  
Obligations of states and political subdivisions | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 0  
Obligations of states and political subdivisions | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 507  
Corporate and other bonds    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 122,232 134,342
Corporate and other bonds | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 32,288  
Corporate and other bonds | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 22,853  
Corporate and other bonds | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 0  
Corporate and other bonds | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 67,091  
Total mortgage-back securities    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 1,241,446 1,313,513
Total mortgage-back securities | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 38,859  
Total mortgage-back securities | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 0  
Total mortgage-back securities | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 1,153,495  
Total mortgage-back securities | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 49,092  
Other securities    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 3,090 $ 3,079
Other securities | Standard & Poor's AAA/AA/A | Moody's AAA/AA/A    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 0  
Other securities | Standard & Poor's BBB/BB/B | Moody's BBB/BB/B    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 0  
Other securities | Standard Poors Not Rated - Agency [Member] | Moody's Not Rated - Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost 1,608  
Other securities | Standard Poors Not Rated - Non-Agency [Member] | Moody's Not Rated - Non-Agency [Member]    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]    
AFS Securities, Amortized Cost $ 1,482