Fair Value Measurements (Narrative) (Details) $ in Thousands, lb in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) derivative_instrument lb $ / lb	Dec. 31, 2019 USD ($) derivative_instrument lb $ / lb	Mar. 31, 2019 USD ($)
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	14.00%
Derivative, number of instruments held | derivative_instrument	1	6
Underlying, derivative mass | $ / lb	0.34	0.37
Derivative, nonmonetary notional amount, mass | lb	2.0	11.2
Derivative liability | $	$ 165	$ 679	$ 200