Nature of Operations and Summary of Significant Accounting Policies - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017	Jul. 01, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 60,177	$ 75,425	$ 85,840	$ 71,487
Restricted cash	975	1,421	2,141	2,082
Total Cash, Cash Equivalents, and Restricted Cash	$ 61,152	$ 76,846	$ 87,981	$ 73,569