Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 23,859	$ 22,730	$ 46,144	$ 43,403
Unrealized gains (losses) on securities available for sale:
Unrealized holding gains (losses) arising during the period, pretax	11,701	(2,012)	17,604	(9,302)
Tax (expense) benefit	(2,714)	471	(4,094)	2,174
Postretirement Plans:
Amortization of unrecognized net actuarial loss	228	51	456	103
Tax benefit	(63)	(12)	(117)	(24)
Other comprehensive income (loss)	9,152	(1,502)	13,849	(7,049)
Comprehensive income	$ 33,011	$ 21,228	$ 59,993	$ 36,354

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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