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Equity (Share-based Payments to Employees, Non-marketable Options, Average Remaining Contractual Life) (Details) - yr
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure of terms and conditions of share-based payment arrangement [Line Items]      
Average remaining contractual life for the outstanding vested options at the end of each period 2.60 2.40 1.91