Income Taxes (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jul. 31, 2016	Dec. 29, 2018	Dec. 30, 2017	Oct. 01, 2018	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Line Items]
Effective income tax rate		(3.00%)	(114.00%)
Income before income taxes		$ 20,423	$ 6,471
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%
Valuation Allowance, Deferred Tax Asset, Explanation of Change		1.8
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent			24.50%
Operating Loss Carryforwards, Limitations on Use		0.8
Unrecognized tax benefits		$ 10,300			$ 9,800
Income tax provision upon recognition of unrecognized tax benefit		10,300
Unrecognized tax benefits that would impact valuation allowance		3,800
Potentail reduction in unrecognized tax benefits and accrued interest over next 12 months		(2,000)
Stockholders' Equity Attributable to Parent		1,321,169	$ 889,099		874,589	$ 885,436
Deferred tax assets		201,149			165,566
Korea
Income Tax Disclosure [Line Items]
Income tax examination, estimate of possible loss	$ 12,000
US Tax on Undistributed Foreign Earnings [Member]
Income Tax Disclosure [Line Items]
Current Federal, State and Local, Tax Expense (Benefit)		1,500	7,100
Net Decrease in Deferred Tax Liability [Member]
Income Tax Disclosure [Line Items]
Deferred Income Tax Expense (Benefit)		14,200
Accounting Standards Update 2016-16
Income Tax Disclosure [Line Items]
Deferred tax assets				$ 75,300
Other Tax Assets				6,000
Other Tax Liabilities				3,000
Accumulated Deficit
Income Tax Disclosure [Line Items]
Stockholders' Equity Attributable to Parent		$ (138,785)	$ (637,519)		$ (599,409)	$ (650,840)
Accumulated Deficit | Accounting Standards Update 2016-16
Income Tax Disclosure [Line Items]
Stockholders' Equity Attributable to Parent				$ 72,300