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