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Share-Based Payments (Weighted Average Assumptions for Employee Stock Purchase Plan and Other Options) (Details) - Employee Stock Purchase Plan [Member]
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Risk-free interest rate 0.10% 0.07% 0.11%
Expected term 6 months 6 months 6 months
Dividend yield 2.00% 2.00% 2.40%
Expected volatility 20.00% 21.00% 19.00%