Subsequent Event - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 28, 2018	Dec. 29, 2017	Dec. 30, 2016	Dec. 28, 2019	Jan. 29, 2019	Oct. 18, 2016	Oct. 20, 2015
Common Stock, Dividends, Per Share, Declared		$ 0.52	$ 0.42	$ 0.36
Stock Repurchase Program, Authorized Amount							$ 35,000,000	$ 35,000,000
PG and E [Member]
Customer Accounts Receivable		$ 5,600,000
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.16
Dividends Payable, Date of Record	Mar. 08, 2019
Stock Repurchase Program, Authorized Amount	$ 75,000,000
Dividends Payable, Date to be Paid	Mar. 22, 2019
Subsequent Event [Member] | PG and E [Member]
Subsequent Cash Receipt Customer Accounts Receivable					$ 2,100,000
Customer Accounts Receivable						$ 6,000,000