Statements of Shareholders' Equity (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Accumulated other comprehensive income (loss)	Dec. 31, 2011 Accumulated other comprehensive income (loss)	Dec. 31, 2010 Accumulated other comprehensive income (loss)	Dec. 31, 2012 Reinvested earnings	Dec. 31, 2011 Reinvested earnings	Dec. 31, 2010 Reinvested earnings	Dec. 31, 2012 Capital in excess of par value	Dec. 31, 2011 Capital in excess of par value	Dec. 31, 2010 Capital in excess of par value
Net of employee benefit funded status adjustment	$ (247)	$ 835	$ (1,426)
Cash dividends (in dollars per share)				$ 0.66	$ 0.6	$ 0.52
Treasury stock, shares re - issued (in shares)							0	0	0