Subsequent Event (Details) - $ / shares		3 Months Ended								12 Months Ended
	Feb. 05, 2019	Dec. 30, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Sep. 24, 2017	Jun. 25, 2017	Mar. 26, 2017	Dec. 30, 2018	Dec. 31, 2017	Dec. 25, 2016
Subsequent Event [Line Items]
Dividends approved (in usd per share)		$ 0.04	$ 0.04	$ 0.04	$ 0.04	$ 0.04	$ 0.08	$ 0.00	$ 0.04	$ 0.16	$ 0.16	$ 0.16
Class B Common Stock | Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends approved (in usd per share)	$ 0.05
Class A Common Stock | Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends approved (in usd per share)	$ 0.05