SECURITIES (Schedule of Gross Unrealized Losses and Fair Value of Investments) (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	$ 1,000,782,000	$ 302,914,000
Less than 12 Months, Unrealized Losses	(21,058,000)	(2,239,000)
More than 12 Months, Fair Value	21,288,000	17,585,000
More than 12 Months, Unrealized Losses	(93,000)	(101,000)
Total, Fair Value	1,022,070,000	320,499,000
Unrealized Losses, Total	(21,151,000)	(2,340,000)
U.S. government and agency securities
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	0	0
Less than 12 Months, Unrealized Losses	0	0
More than 12 Months, Fair Value	4,899,000	5,456,000
More than 12 Months, Unrealized Losses	(47,000)	(52,000)
Total, Fair Value	4,899,000	5,456,000
Unrealized Losses, Total	(47,000)	(52,000)
Obligations of states and political subdivisions
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	271,172,000	5,091,000
Less than 12 Months, Unrealized Losses	(4,956,000)	(18,000)
More than 12 Months, Fair Value	0	0
More than 12 Months, Unrealized Losses	0	0
Total, Fair Value	271,172,000	5,091,000
Unrealized Losses, Total	(4,956,000)	(18,000)
Corporate and other bonds
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	42,612,000	17,946,000
Less than 12 Months, Unrealized Losses	(237,000)	(52,000)
More than 12 Months, Fair Value	4,785,000	10,698,000
More than 12 Months, Unrealized Losses	(6,000)	(47,000)
Total, Fair Value	47,397,000	28,644,000
Unrealized Losses, Total	(243,000)	(99,000)
Commercial
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	92,444,000	23,547,000
Less than 12 Months, Unrealized Losses	(1,724,000)	(19,000)
More than 12 Months, Fair Value	359,000	376,000
More than 12 Months, Unrealized Losses	(1,000)	0
Total, Fair Value	92,803,000	23,923,000
Unrealized Losses, Total	(1,725,000)	(19,000)
Residential
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	594,554,000	256,330,000
Less than 12 Months, Unrealized Losses	(14,141,000)	(2,150,000)
More than 12 Months, Fair Value	11,245,000	1,055,000
More than 12 Months, Unrealized Losses	(39,000)	(2,000)
Total, Fair Value	605,799,000	257,385,000
Unrealized Losses, Total	(14,180,000)	(2,152,000)
Agency | Commercial
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	65,708,000	5,893,000
Less than 12 Months, Unrealized Losses	(1,614,000)	(2,000)
More than 12 Months, Fair Value	359,000	376,000
More than 12 Months, Unrealized Losses	(1,000)	0
Total, Fair Value	66,067,000	6,269,000
Unrealized Losses, Total	(1,615,000)	(2,000)
Agency | Residential
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	558,523,000	219,388,000
Less than 12 Months, Unrealized Losses	(13,650,000)	(1,944,000)
More than 12 Months, Fair Value	1,175,000	1,055,000
More than 12 Months, Unrealized Losses	(18,000)	(2,000)
Total, Fair Value	559,698,000	220,443,000
Unrealized Losses, Total	(13,668,000)	(1,946,000)
Non-agency | Commercial
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	26,736,000	17,654,000
Less than 12 Months, Unrealized Losses	(110,000)	(17,000)
More than 12 Months, Fair Value	0	0
More than 12 Months, Unrealized Losses	0	0
Total, Fair Value	26,736,000	17,654,000
Unrealized Losses, Total	(110,000)	(17,000)
Non-agency | Residential
Debt and Equity Securities, FV-NI [Line Items]
Less than 12 months, Fair Value	36,031,000	36,942,000
Less than 12 Months, Unrealized Losses	(491,000)	(206,000)
More than 12 Months, Fair Value	10,070,000	0
More than 12 Months, Unrealized Losses	(21,000)	0
Total, Fair Value	46,101,000	36,942,000
Unrealized Losses, Total	$ (512,000)	$ (206,000)