Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net income	$ 37,433	$ 35,113	$ 117,575	$ 70,194
Securities available for sale:
Unrealized net holding (losses) gains arising during the period, gross	(7,426)	(1,263)	(21,329)	26,509
Tax effect	1,857	316	5,332	(6,627)
Unrealized net holding (losses) gains arising during the period, net	(5,569)	(947)	(15,997)	19,882
Reclassification adjustment for net gains in net income, gross	0	0	0	(3)
Tax effect	0	0	0	1
Reclassification adjustment for net gains in net income, net	0	0	0	(2)
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, gross	149	157	434	495
Tax effect	(38)	(39)	(109)	(124)
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, net	111	118	325	371
Total securities available for sale, net	(5,458)	(829)	(15,672)	20,251
Cash flow hedges:
Unrealized losses on derivatives (cash flow hedges), gross	0	0	0	(274)
Tax effect	0	0	0	69
Unrealized losses on derivatives (cash flow hedges), net	0	0	0	(205)
Reclassification of net unrealized losses on cash flow hedges to interest (income), gross	0	101	21	192
Tax effect	0	(25)	(5)	(48)
Reclassification of net unrealized losses on cash flow hedges to interest (income), net	0	76	16	144
Total cash flow hedges, net	0	76	16	(61)
Pension and other benefits:
Amortization of prior service cost and actuarial losses, gross	344	381	996	1,143
Tax effect	(86)	(95)	(249)	(286)
Amortization of prior service cost and actuarial losses, net	258	286	747	857
Total pension and other benefits, net	258	286	747	857
Total other comprehensive (loss) income	(5,200)	(467)	(14,909)	21,047
Comprehensive income	$ 32,233	$ 34,646	$ 102,666	$ 91,241