Statements of Cash Flows (Cash Flow Supplemental Disclosures) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018
Interest Paid, Excluding Capitalized Interest, Operating Activities		$ 19,261	$ 15,449
Federal income tax		42,000	7,193
Operating cash flows from operating leases	[1]	6,062	0
Operating cash flows from financing leases		12	0
Financing cash flows from finance leases		811	4,891
Assets acquired under finance lease arrangements		824
Assets acquired under finance lease arrangements			4,114
Assets acquired under operating lease arrangements	[1]	13,648	0
Non-cash purchase of property and equipment		108	0
AFS Fixed Income Securities [Member]
Corporate actions related to securities	[2]	29,771	32,757
Equity Securities [Member]
Corporate actions related to securities	[2]	$ 14,250	$ 944

[1] Upon adoption of ASU 2016-02, effective January 1, 2019, we are required to disclose cash paid for amounts included in the measurement of operating lease liabilities, as well as supplemental non-cash information on operating lease liabilities arising from obtaining operating lease assets.

[2] Examples of such corporate actions include exchanges, non-cash acquisitions, and stock splits.