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Statements of Cash Flow (Cash Flow Supplemental Disclosures) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Interest	$ 15,449	$ 15,356
Federal income tax	7,193	39,000
Assets acquired under capital lease arrangements	4,114	278
Cash	446		$ 534
Restricted cash	12,386		44,176
Total cash and restricted cash shown in the Statements of Cash Flows	12,832	18,659	$ 44,710	$ 37,405
AFS Fixed Income Securities [Member]
Corporate actions related to securities	32,757	6,192
Equity Securities [Member]
Corporate actions related to securities	$ 944	$ 4,725

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The increase during the period in capital lease obligations due to entering into new capital leases.

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