Commitments and Contingencies (Insurance) (Details) - USD ($)		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017
Insurance
Insurance maximum coverage per incident		$ 300,000,000
Insurance maximum coverage per property		300,000,000
All Risk Property And Rental Value
Insurance
Insurance maximum coverage per incident		1,700,000,000.0
Terrorism Coverage Including NBCR
Insurance
Insurance maximum coverage per incident		$ 1,700,000,000.0
Insurance coverage end date		Dec. 01, 2020
Insurance maximum coverage in aggregate		$ 1,700,000,000.0
FNSIC | NBCR
Insurance
Insurance deductible		$ 293,000
Self Insured Responsibility (in percentage)		17.00%
Federal Government Responsibility (in percentage)		83.00%
FNSIC | NBCR | Subsequent Event
Insurance
Insurance deductible	$ 306,000
Self Insured Responsibility (in percentage)	18.00%
Federal Government Responsibility (in percentage)	82.00%