Capital Stock Par Value of Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 10, 2004
Class of Stock [Line Items]
Stockholders' Equity Note, Percent of Entity Owned by Current and Retired Employees	100.00%
Common stock stated value per share (USD per share)	$ 20	$ 20
Common stock, subscriptions ( in shares)	878,608
Common shares subscribed (in dollars)	$ 17,572
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Shares of common stock purchased	718,269	752,983	638,647
Shares of common stock retired	666,861	780,077	681,637
Preferred stock shares authorized				10,000,000
Preferred stock par or stated value per share (USD per share)				$ 0.01
Preferred stock outstanding (in shares)	0	0
Common stock dividend declared, percent	2.50%	0.00%	2.50%
Common Stock
Class of Stock [Line Items]
Percentage Ownership in Voting Trust	83.00%