Capital Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Capital Stock [Abstract]
Percent of stock owned by active and retired employees			100.00%
Percent of shares held in voting trust	83.00%		83.00%
Common stock stated value per share	$ 20.00		$ 20.00		$ 20.00
Cash dvidends	$ 6.8	$ 6.8	$ 13.7	$ 13.7
Preferred stock shares authorized	10,000,000		10,000,000
Preferred stock par or stated value per share (USD per share)	$ 0.01		$ 0.01
Preferred stock outstanding (in shares)	0		0		0