Fair Value Measurements (Narrative) (Details) lb in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) lb $ / lb
Fair Value Disclosures [Abstract]
Number of years long-term sales growth forecasted over	6 years
Average long-term sales growth forecast, over next 4 years, percent per year	12.00%
Derivative nonmonetary notional amount, mass | lb	12.0
Underlying derivative mass | $ / lb	0.25
Derivative asset | $	$ 0.9