Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net income	$ 40,296	$ 24,713	$ 80,142	$ 35,081
Securities available for sale:
Unrealized net holding gains (losses) arising during the period, gross	9,408	6,433	(13,903)	27,772
Tax effect	(2,352)	(1,608)	3,475	(6,943)
Unrealized net holding gains (losses) arising during the period, net	7,056	4,825	(10,428)	20,829
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	143	165	285	338
Tax effect	(36)	(42)	(71)	(85)
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, net	107	123	214	253
Total securities available for sale, net	7,163	4,948	(10,214)	21,080
Cash flow hedges:
Unrealized losses on derivatives (cash flow hedges), gross	0	(19)	0	(274)
Tax effect	0	5	0	69
Unrealized losses on derivatives (cash flow hedges), net	0	(14)	0	(205)
Reclassification of net unrealized losses on cash flow hedges to interest (income), gross	0	81	21	91
Tax effect	0	(20)	(5)	(23)
Reclassification of net unrealized losses on cash flow hedges to interest (income), net	0	61	16	68
Total cash flow hedges, net	0	47	16	(137)
Pension and other benefits:
Amortization of prior service cost and actuarial losses, gross	326	381	652	762
Tax effect	(82)	(96)	(163)	(191)
Amortization of prior service cost and actuarial losses, net	244	285	489	571
Total pension and other benefits, net	244	285	489	571
Total other comprehensive income (loss)	7,407	5,280	(9,709)	21,514
Comprehensive income	$ 47,703	$ 29,993	$ 70,433	$ 56,595