Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net income	$ 39,126	$ 39,846
Securities available for sale:
Unrealized net holding (losses) arising during the period, gross	(91,030)	(23,311)
Tax effect	22,758	5,827
Unrealized net holding (losses) arising during the period, net	(68,272)	(17,484)
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, gross	137	142
Tax effect	(35)	(35)
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, net	102	107
Total securities available for sale, net	(68,170)	(17,377)
Cash flow hedges:
Reclassification of net unrealized losses on cash flow hedges to interest expense, gross	0	21
Tax effect	0	(5)
Reclassification of net unrealized losses on cash flow hedges to interest expense, net	0	16
Total cash flow hedges, net	0	16
Pension and other benefits:
Amortization of prior service cost and actuarial losses, gross	186	326
Tax effect	(47)	(81)
Amortization of prior service cost and actuarial losses, net	139	245
Total pension and other benefits, net	139	245
Total other comprehensive (loss)	(68,031)	(17,116)
Comprehensive (loss) income	$ (28,905)	$ 22,730