Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Jan. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax benefit	$ 623	$ (10,358)
Effective tax rate (as a percent)	(1.40%)
Deferred tax benefit from tax reform remeasurement	$ 10,100
Effective income tax rate excluding revaluation of deferred taxes (as a percent)	20.90%
Effective income tax rate excluding excess tax benefit and TCJA impacts (as a percent)	28.00%	32.80%
Liability for uncertain tax positions	$ 9,400			$ 9,300
Period during which unrecognized tax benefits would affect the effective tax rate	12 months
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefit	$ 3,200			$ 1,800
Scenario, Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Statutory federal tax rate			24.50%