CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total		Common Shares	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2017	$ 311,545		$ 423,856	$ 33,309	$ (127,740)	$ (17,880)
Balance (in shares) at Dec. 31, 2017			34,595
Net income	37,465	[1]			37,465
Redeemable noncontrolling interest redemption value adjustment	1,781	[1]			1,781
Acquisition of noncontrolling interest	14,401			14,401
Acquisition of noncontrolling interest (in shares)			213
Common shares issued under stock plans (in shares)			228
Common shares withheld for taxes on vested stock awards	(3,483)			(3,483)
Common shares withheld for taxes on vested stock awards (in shares)			(63)
Repurchases of common shares	(3,765)			(3,765)
Repurchases of common shares (in shares)			(57)
Share-based compensation	5,475			5,475
Adoption of ASU 2016-16 | ASU 2016-16	(2,242)				(2,242)
Other comprehensive income, net of tax	(1,504)					(1,504)
Balance at Sep. 28, 2018	359,673		$ 423,856	45,937	(90,736)	(19,384)
Balance (in shares) at Sep. 28, 2018			34,916
Balance at Jun. 29, 2018	324,365		$ 423,856	31,793	(112,167)	(19,117)
Balance (in shares) at Jun. 29, 2018			34,671
Net income	14,554	[1]			14,554
Redeemable noncontrolling interest redemption value adjustment	6,877	[1]			6,877
Acquisition of noncontrolling interest	14,401			14,401
Acquisition of noncontrolling interest (in shares)			213
Common shares issued under stock plans (in shares)			62
Common shares withheld for taxes on vested stock awards	(116)			(116)
Common shares withheld for taxes on vested stock awards (in shares)			(2)
Repurchases of common shares	(1,836)			(1,836)
Repurchases of common shares (in shares)			(28)
Share-based compensation	1,695			1,695
Other comprehensive income, net of tax	(267)					(267)
Balance at Sep. 28, 2018	359,673		$ 423,856	45,937	(90,736)	(19,384)
Balance (in shares) at Sep. 28, 2018			34,916
Balance at Dec. 31, 2018	368,255		$ 423,856	46,018	(79,092)	(22,527)
Balance (in shares) at Dec. 31, 2018			34,886
Net income	31,556	[2]			31,556
Common shares issued for business combination	10,900			10,900
Common shares issued for business combination (in shares)			124
Common shares issued under stock plans	425			425
Common shares issued under stock plans (in shares)			245
Common shares withheld for taxes on vested stock awards	(6,839)			(6,839)
Common shares withheld for taxes on vested stock awards (in shares)			(85)
Repurchases of common shares	(6,684)			(6,684)
Repurchases of common shares (in shares)			(81)
Share-based compensation	7,348			7,348
Other comprehensive income, net of tax	(2,084)					(2,084)
Balance at Sep. 27, 2019	402,877		$ 423,856	51,168	(47,536)	(24,611)
Balance (in shares) at Sep. 27, 2019			35,089
Balance at Jun. 28, 2019	386,182		$ 423,856	41,065	(56,459)	(22,280)
Balance (in shares) at Jun. 28, 2019			34,972
Net income	8,923	[2]			8,923
Common shares issued for business combination	10,900			10,900
Common shares issued for business combination (in shares)			124
Common shares issued under stock plans	425			425
Common shares issued under stock plans (in shares)			36
Common shares withheld for taxes on vested stock awards	(120)			(120)
Common shares withheld for taxes on vested stock awards (in shares)			(1)
Repurchases of common shares	(3,345)			(3,345)
Repurchases of common shares (in shares)			(42)
Share-based compensation	2,243			2,243
Other comprehensive income, net of tax	(2,331)					(2,331)
Balance at Sep. 27, 2019	$ 402,877		$ 423,856	$ 51,168	$ (47,536)	$ (24,611)
Balance (in shares) at Sep. 27, 2019			35,089

[1] 53,968 performance-based restricted stock units granted to certain members of the executive management team and 213,219 shares of restricted stock issued to Laser Quantum former non-controlling interest holders were considered contingently issuable shares and were excluded from the calculation of the denominator as the contingent conditions had not been met as of September 28, 2018.

[2] 47,147 performance-based restricted stock units granted to certain members of the executive management team and 213,219 shares of restricted stock issued to Laser Quantum former non-controlling interest holders are considered contingently issuable shares and were excluded from the calculation of the denominator as the contingent conditions had not been met as of September 27, 2019.