Net Income Per Share - Summary of Reconciliation of Numerators and Denominators of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017	Dec. 31, 2017
Basic net income per share:
Net income	$ 37,500	$ 31,486	$ 145,833	$ 118,741	$ 158,440
Weighted average shares outstanding	126,855	134,320	129,572	136,063
Basic net income per share	$ 0.30	$ 0.23	$ 1.13	$ 0.87
Diluted net income per share:
Net income	$ 37,500	$ 31,486	$ 145,833	$ 118,741	$ 158,440
Weighted average shares outstanding - basic	126,855	134,320	129,572	136,063
Dilutive effect of equity-based awards:
Assumed exercise of options to purchase shares	341	2,128	484	2,506
Weighted average shares and equivalent shares outstanding	127,627	136,770	130,537	138,860
Diluted net income per share	$ 0.29	$ 0.23	$ 1.12	$ 0.86
RSUs [Member]
Dilutive effect of equity-based awards:
Dilutive effect	175	122	193	124
RSAs [Member]
Dilutive effect of equity-based awards:
Dilutive effect	82	114	137	102
PSAs [Member]
Dilutive effect of equity-based awards:
Dilutive effect	174	86	151	65