Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 28,194	$ 18,180
Unrealized gains (losses) on securities available for sale:
Unrealized holding gains (losses) arising during the period, pretax	(24,235)	20,765
Tax (expense) benefit	5,569	(4,772)
Postretirement Plans:
Amortization of unrecognized net actuarial loss	171	178
Tax benefit	(40)	(41)
Other comprehensive income (loss)	(18,535)	16,130
Comprehensive income	$ 9,659	$ 34,310

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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