Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Jan. 01, 2017	$ 672,909	$ 140	$ 597,269	$ 75,500
Beginning Balance, Shares at Jan. 01, 2017		140,002,242
Net income	158,440			158,440
Other comprehensive income (loss)	(784)				$ (784)
Issuance of shares under stock plans	9,300	$ 2	9,298
Issuance of shares under stock plans, Shares		2,144,669
Repurchase and retirement of common stock	(203,392)	$ (10)		(203,382)
Repurchase and retirement of common stock, Shares		(9,696,819)
Equity-based compensation	14,221		14,221
Ending Balance at Dec. 31, 2017	650,694	$ 132	620,788	30,558	(784)
Ending Balance, Shares at Dec. 31, 2017		132,450,092
Net income	66,624			66,624
Other comprehensive income (loss)	3,320				3,320
Issuance of shares under stock plans	6,877	$ 2	6,875
Issuance of shares under stock plans, Shares		2,292,511
Repurchase and retirement of common stock	$ (83,000)	$ (3)		(82,997)
Repurchase and retirement of common stock, Shares	(3,329,409)	(3,329,409)
Equity-based compensation	$ 3,968		3,968
Ending Balance at Apr. 01, 2018	$ 648,483	$ 131	$ 631,631	$ 14,185	$ 2,536
Ending Balance, Shares at Apr. 01, 2018		131,413,194