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Stock-Based Compensation, Stock Option Valuation Assumptions (Details) - Stock Options [Member] - $ / shares
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Fair Value Assumptions [Abstract]      
Weighted average grant date fair value of grants (in dollars per share) $ 18.84 $ 12.59 $ 16.26
Risk-free interest rate [1] 2.10% 1.40% 1.70%
Dividend yield [2] 2.50% 2.30% 2.10%
Expected volatility [3] 48.20% 47.90% 46.80%
Expected life in months [4] 68 months 68 months 65 months
[1] The risk-free interest rate is based upon the rate on a zero coupon U.S. Treasury bill, for periods within the contractual life of the option, in effect at the time of the grant.
[2] The dividend yield is based on the average of historical stock prices and actual dividends paid.
[3] Expected volatility is based on the historical volatility of the Company's stock price, over a period similar to the expected life of the option.
[4] The expected term of the option is based on the historical employee exercise behavior, the vesting terms of the respective option, and a contractual life of either seven or ten years.