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Stock Plans (Details 2) - Stock Option [Member] - $ / shares
2 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Weighted Average Assumptions Used        
Dividend yield 1.58% 1.80% 1.90% 1.10%
Expected volatility 21.41% 24.00% 25.00% 37.00%
Risk-free interest rate 2.26% 2.30% 1.50% 1.70%
Expected life of stock option (in years) 7 years 6 years 11 months 6 years 4 months 6 years 8 months
Weighted-average fair value per option $ 19.18 $ 18.18 $ 13.67 $ 29.2