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Stockholders' Equity Stockholders' Equity (Assumptions using the Black-Scholes option pricing model) (Details) - Employee Stock Option
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected dividend yield 0.40% 0.50% 0.60%
Expected volatility 32.62% 33.34% 33.63%
Risk-free interest rate 1.13% 0.99% 0.41%
Expected life (years) 3 years 7 months 6 days 3 years 8 months 12 days 3 years 7 months 6 days