Investments - Madison Financial Statements (Details) - Madison Paper Industries - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2019	Dec. 30, 2018	Dec. 31, 2017
Balance Sheet Information [Abstract]
Current assets	$ 15,337	$ 18,374
Total assets	15,337	18,374
Current liabilities	570	3,336
Total liabilities	570	3,336
Total equity	14,767	15,038
Income Statement Information [Abstract]
Cost of sales	0	0	$ (13,396)
General and administrative income/(expense) and other	(318)	(1,280)	55,058
Total operating (expense)/income	(318)	(1,280)	41,662
Other income	46	122	18
Net (loss)/income	$ (272)	$ (1,158)	$ 41,680