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Statements of Cash Flow (Cash Flow Supplemental Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest	$ 28,930	$ 30,464	$ 25,089
Federal income tax	100,000	47,000	55,825
Operating cash flows from operating leases	7,935	9,498	8,138
Operating cash flows from financing leases	35	15	16
Financing cash flows from financing leases	1,768	550	977
Assets acquired under finance lease arrangements	6,709	324	824
Assets acquired under operating lease arrangements	3,272	22,390	13,808
Non-cash purchase of property and equipment	472	590	89
Available-for-sale Securities [Member]
Corporate actions related to securities	56,365	55,446	61,369
Held-to-maturity Securities [Member]
Corporate actions related to securities	0	2,589	0
Equity Securities [Member]
Corporate actions related to securities	30,666	10,890	14,250
Conversion of AFS fixed income securities to equity securities	$ 15,139	$ 0	$ 0

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