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Statements of Cash Flows (Cash Flow Supplemental Disclosures) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Interest		$ 8,722	$ 8,854
Federal income tax		0	0
Operating cash flows from operating leases		2,226	2,130
Operating cash flows from financing leases		2	6
Financing cash flows from finance leases		115	142
Assets acquired under finance lease arrangements		183	29
Assets acquired under operating lease arrangements		16	3,828
Non-cash purchase of property and equipment		3	5
Available-for-sale Securities
Corporate actions related to securities	[1]	26,085	8,040
Held-to-maturity Securities [Member]
Corporate actions related to securities	[1]	$ 0	$ 2,596
[1] Examples of corporate actions include exchanges, non-cash acquisitions, and stock splits.

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Amount of cash paid for interest, including, but not limited to, capitalized interest and payment to settle zero-coupon bond attributable to accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount; classified as operating and investing activities.

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