Options and Awards Valuation Assumptions (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assumptions and Methodology
Options Granted	481	497	637
Weighted Average Risk-Free Rate	2.00%	1.40%	1.70%
Expected Life	6 years 2 months	6 years 4 months	6 years 6 months
Weighted Average Volatility	35.20%	37.80%	39.50%
Weighted Average Dividend Yield	0.80%	0.80%	0.60%