Other Comprehensive Income (Components of OCI) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Unrealized gains and losses on available for sale debt securities:
Net unrealized (losses) gains arising during the period	$ (12,152)	$ 22,563
Reclassification adjustment for gains included in net income	(230)	0
Total	(12,382)	22,563
Unrealized gains (losses) on derivatives (cash flow hedges)	6,226	(7,697)
Amortization related to post-retirement obligations	(150)	112
Total other comprehensive (loss) income	(6,306)	14,978
Unrealized gains and losses on available for sale debt securities:
Net unrealized (losses) gains arising during the period	3,133	(5,817)
Reclassification adjustment for gains included in net income	59	0
Total	3,192	(5,817)
Unrealized gains (losses) on derivatives (cash flow hedges)	(1,605)	1,984
Amortization related to post-retirement obligations	41	(28)
Total other comprehensive (loss) income	1,628	(3,861)
Unrealized gains and losses on available for sale debt securities:
Net unrealized (losses) gains arising during the period	(9,019)	16,746
Reclassification adjustment for gains included in net income	(171)	0
Total	(9,190)	16,746
Unrealized gains (losses) on derivatives (cash flow hedges)	4,621	(5,713)
Amortization related to post-retirement obligations	(109)	84
Total other comprehensive (loss) income	$ (4,678)	$ 11,117