Segment Information - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net realized securities gains	$ 23,028	$ 29,542	$ 62,957
Interest	107,859	108,703	115,804
Corporate and other
Segment Reporting Information [Line Items]
Net realized securities gains	23,000	16,400	63,000
National Beef
Segment Reporting Information [Line Items]
Interest	6,700	12,900	16,600
Parent Company
Segment Reporting Information [Line Items]
Interest	58,943	58,881	87,181
All other
Segment Reporting Information [Line Items]
Interest	$ 42,200	$ 36,900	$ 12,000
U.S. | Geographic Concentration Risk | Revenue | National Beef
Segment Reporting Information [Line Items]
Concentration risk, percentage	88.80%	89.20%	89.50%