Capital Stock - Captial Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Equity [Abstract]
Percent of entity owned by current and retired employees	100.00%
Percent of entity held in voting trust	83.00%
Common, stated value (in dollars per share)	$ 20		$ 20
Dividends, Common Stock, Cash	$ 4,983	$ 4,815