ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Reclassifications out of Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Amounts Reclassified from AOCI
Interest expense	$ 7,952	$ 10,192
Income tax (expense) benefit	(2,676)	(3,415)
Net income	9,348	12,927
Amount Reclassified from Accumulated Other Comprehensive Income
Amounts Reclassified from AOCI
Total reclassifications, before income tax	(43)	427
Income tax (expense) benefit	13	(125)
Net income	(30)	302
Amount Reclassified from Accumulated Other Comprehensive Income | Realized losses on sale of available for sale securities | Net securities gains (losses)
Amounts Reclassified from AOCI
Net securities gains (losses)	(15)
Amount Reclassified from Accumulated Other Comprehensive Income | Prior service credit | Other operating expense
Amounts Reclassified from AOCI
Other operating expenses	19	19
Amount Reclassified from Accumulated Other Comprehensive Income | Actuarial losses | Other operating expense
Amounts Reclassified from AOCI
Other operating expenses	(157)	(148)
Amount Reclassified from Accumulated Other Comprehensive Income | Realized gains on cash flow hedges | Interest expense.
Amounts Reclassified from AOCI
Interest expense	$ 110	$ 556