Income Taxes (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017	Dec. 30, 2017
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Income tax provision (benefit)	$ 1,343,000	$ 47,000	$ 1,940,000	$ 565,000
Unrecognized tax benefits that could significantly change during the next twelve months	1,500,000		1,500,000
Unrecognized tax benefits, associated interest and penalties that could significantly change within the next twelve months	100,000		100,000
Total potential decrease in UTB	1,600,000		1,600,000
Tax credit carryforward, amount					$ 59,200,000
Deferred tax assets, valuation allowance	24,500,000		24,500,000
Bermuda
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Income tax provision (benefit)			$ 0
Statutory income tax rate			0.00%
Federal
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating loss carryforwards					351,400,000
Tax credit carryforward, amount					50,200,000
State and Local Jurisdiction
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating loss carryforwards					162,900,000
Tax credit carryforward, amount					59,200,000
Other Long-term Liabilities
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Uncertain tax positions	$ 26,600,000		$ 26,600,000		26,900,000
No Expiration Date
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Tax credit carryforward, amount					$ 57,900,000