Summary of Significant Accounting Policies - Net income per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Oct. 01, 2019	Jul. 02, 2019	Apr. 02, 2019	Jan. 01, 2019	Oct. 02, 2018	Jul. 03, 2018	Apr. 03, 2018	Dec. 31, 2019	Jan. 01, 2019	Jan. 02, 2018
Net income per share, basic and diluted
Net income	$ 48,709	$ 16,090	$ 35,510	$ 26,984	$ 16,178	$ 28,475	$ 28,353	$ 26,029	$ 127,293	$ 99,035	$ 157,392
Basic weighted average shares outstanding (in shares)									43,949	45,263	46,930
Dilutive effect of equity awards (in shares)									596	952	1,222
Diluted weighted average shares outstanding (in shares)									44,545	46,215	48,152
Basic net income per share (in dollars per share)	$ 1.11	$ 0.37	$ 0.80	$ 0.61	$ 0.36	$ 0.63	$ 0.62	$ 0.57	$ 2.90	$ 2.19	$ 3.35
Diluted net income per share (in dollars per share)	$ 1.10	$ 0.36	$ 0.79	$ 0.60	$ 0.35	$ 0.61	$ 0.61	$ 0.56	$ 2.86	$ 2.14	$ 3.27
Common Stock
Net income per share, basic and diluted
Antidilutive securities excluded from calculation of basic earnings per share (in shares)									2,300	1,500	1,600
Restricted Shares and Restricted Share Units
Net income per share, basic and diluted
Antidilutive securities excluded from calculation of basic earnings per share (in shares)									1,800	1,700	1,700