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Employee Stock and Savings Plans - Schedule of Estimation Assumptions Used (Details)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Expected life 6 years 3 months 18 days 6 years 3 months 6 years 4 months 24 days
Average risk-free interest rate 2.20% 2.20% 1.90%
Expected volatility (as a percent) 28.30% 28.90% 29.30%
Expected dividend yield (as a percent) 0.00% 0.00% 0.00%