Loans to and Investments in Associated Companies (National Beef) (Narrative) (Details) - USD ($) $ in Thousands	Jun. 05, 2018	Sep. 30, 2018	Jun. 04, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Investment in associated company		$ 2,450,901		$ 2,066,829	$ 2,350,980	$ 2,125,098
National Beef
Schedule of Equity Method Investments [Line Items]
Percentage of ownership owned			79.00%
Equity method investment, ownership percentage	31.00%	31.00%
Investment in associated company	$ 592,300	$ 626,870		$ 0
Weighted average useful life	15 years
National Beef | Discontinued operations, disposed of by sale
Schedule of Equity Method Investments [Line Items]
Percentage of ownership owned	48.00%
National Beef
Schedule of Equity Method Investments [Line Items]
Enterprise value	$ 2,300,000
Percentage of ownership owned		100.00%
Equity valuation	$ 1,900,000