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Statements of Cash Flow (Cash Flow Supplemental Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest	$ 22,098	$ 21,892	$ 22,221
Federal income tax	46,405	39,500	22,699
Corporate actions related to equity securities, AFS	3,263	4,239	334
Assets acquired under capital lease arrangements	3,151	6,760	5,642
Non-cash purchase of property and equipment	78	0	338
AFS Fixed Income Securities [Member]
Exchange of fixed income securities	23,579	36,792	20,781
Held-to-maturity Securities [Member]
Exchange of fixed income securities	0	15,257	$ 4,289
National Flood Insurance Program [Member]
Restricted cash	$ 36,900	$ 11,900

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- Definition

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

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