Stockholders' Equity (Schedule of Reclassifications Out Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2017	Oct. 01, 2017	Jul. 02, 2017	Apr. 02, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Net revenue	$ 288,928	$ 269,411	$ 255,276	$ 245,201	$ 274,149	$ 251,950	$ 251,685	$ 261,385	$ 1,058,816	$ 1,039,169	[1]	$ 1,143,445	[1]
Cost of revenue									717,118	731,453		769,543
Research and development									82,416	71,893		70,904
Sales and marketing									152,569	138,679		139,591
General and administrative									64,857	54,346		53,996
Income from continuing operations before income taxes									43,204	46,224		106,495
Provision for income taxes	19,210	5,483	1,271	(86)	48,496	950	3,061	4,850	25,878	57,357		36,183
Net income (loss) from continuing operations	(535)	16,310	533	1,018	(41,778)	9,624	9,989	11,032	17,326	(11,133)		70,312
Net income (loss) from discontinued operations, net of tax									(35,655)	30,569		5,539
Net income (loss)	$ (27,839)	$ 9,150	$ (5,230)	$ 5,590	$ (31,934)	$ 20,794	$ 14,582	$ 15,994	(18,329)	19,436		75,851
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Net revenue									665	(5,786)		850
Cost of revenue									(9)	18		(6)
Research and development									83	130		(55)
Sales and marketing									(102)	788		(189)
General and administrative									(53)	133		(30)
Income from continuing operations before income taxes									584	(4,717)		570
Provision for income taxes									(123)	1,651		(200)
Net income (loss) from continuing operations									461	(3,066)		370
Net income (loss) from discontinued operations, net of tax									4	(1,890)		163
Net income (loss)									$ 465	$ (4,956)		$ 533

[1] Prior period amounts have not been adjusted to conform with ASC 606 as the Company adopted ASC 606 under the modified retrospective method.