Long-term Debt - Convertible Senior Notes (Additional Notes) (Details) $ / shares in Units, $ in Thousands, shares in Millions		9 Months Ended
	Sep. 11, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 28, 2018 $ / shares
Debt Instrument [Line Items]
Proceeds from issuance of convertible notes		$ 143,750	$ 0
Maturity date		Sep. 15, 2023
Closing price of common stock (in dollars per share) | $ / shares				$ 26.65
Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Net proceeds to repurchase common stock	$ 38,800
Purchases of treasury stock and buyback of shares for taxes (in shares) | shares	(1.3)
Cost of hedging transactions	$ 8,600
Convertible Debt | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Interest rate stated, percentage	2.375%
Aggregated principal amount	$ 143,800
Initial purchasers' discount and issuance costs	(4,400)
Proceeds from debt, net of issuance costs	$ 139,400
Shares conversion rate		26.5957
Initial conversion price (in dollars per share) | $ / shares	$ 37.60
Initial liability component of note		$ 122,900
Debt borrowing rate, percentage		5.70%
Debt discount for conversion option		$ 20,900
Deferred Tax Liability, Convertible Debt		5,400
Unamortized debt issuance costs		(3,996)
Debt Issuance Costs, Gross		4,700
Deferred finance cost, attributable liability component		4,000
Deferred finance costs, equity component		700
Deferred tax asset, convertible debt equity component		$ 200
Remaining discount weighted-average remaining period (years)		5 years
Revolving Credit Facility | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Net proceeds to pay down revolving credit facility	$ 49,000