Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 25,019	$ 21,991	$ 71,163	$ 65,394
Unrealized gains (losses) on securities available for sale:
Unrealized holding gains (losses) arising during the period, pretax	2,210	(927)	19,814	(10,229)
Tax (expense) benefit	(508)	216	(4,602)	2,390
Reclassification to realized (gains) losses	(97)	0	(97)	0
Tax expense (benefit)	22	0	22	0
Postretirement Plans:
Amortization of unrecognized net actuarial loss	155	(87)	611	16
Tax benefit	(36)	20	(153)	(4)
Other comprehensive income (loss)	1,746	(778)	15,595	(7,827)
Comprehensive income	$ 26,765	$ 21,213	$ 86,758	$ 57,567

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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