Consolidated Statements of Comprehensive Earnings - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net earnings	$ 150,638	$ 120,371	$ 104,774
OTHER ITEMS OF COMPREHENSIVE EARNINGS (LOSS):
Change in unrealized gain (loss) on investment securities available-for-sale, before income tax	(38,185)	23,266	(44,679)
Reclassification adjustment for realized losses (gains) on investment securities included in net earnings, before income tax	(1,354)	(1,828)	(1,270)
Minimum liability pension adjustment, before income tax	1,970	257	1,410
Total other items of comprehensive earnings (losses)	(37,569)	21,695	(44,539)
Income tax benefit (expense) related to: Investment securities
Investment securities	8,303	(13,774)	16,082
Minimum liability pension adjustment	(414)	420	(493)
Total income tax benefit (expense)	7,889	(13,354)	15,589
COMPREHENSIVE EARNINGS	$ 120,958	$ 128,712	$ 75,824

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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