Quarterly report pursuant to Section 13 or 15(d)

Debt and Secured Revolving Line of Credit (Convertible Debt) (Details)

v3.8.0.1
Debt and Secured Revolving Line of Credit (Convertible Debt) (Details) - 2.125% Convertible Senior Notes due 2026 - USD ($)
Mar. 31, 2018
Dec. 30, 2017
Dec. 31, 2016
Sep. 28, 2016
Sep. 14, 2016
Debt Instrument [Line Items]          
Principal $ 805,000,000 $ 805,000,000   $ 105,000,000 $ 700,000,000
Unamortized debt discount (280,000,000) (286,000,000)      
Unamortized debt issuance costs (12,000,000) (12,000,000)      
Net carrying amount 513,000,000 507,000,000      
Carrying amount of the equity component, net 305,000,000 $ 305,000,000      
Equity issuance costs $ 9,000,000   $ 9,000,000