Common Stock (details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common Stock Shares Authorized	100,000,000	100,000,000
Reserved Shares Employee Stock Purchase Plan	122,184
Reserved Shares Dividend Reinvestment	96,991
Reserved Shares Stock Options	492,150	529,925	579,225	490,460
Date Through Which Entity May Repurchase Stock Under Board Authorization	May 2014
Aggregate Authorized Shares To Repurchase	2,800,000
Aggregate Authorized Value Of Shares To Repurchase	$ 100,000,000
Treasury Stock, Shares	2,100,000.0
Treasury Stock Program	$ 83,300,000.0
Common Stock Shares Issued Table [Abstract]
Common Stock, Shares, Outstanding	27,075,000	26,917,000	26,756,000	26,668,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans	16,000	18,000	15,000
Stock Issued During Period, Shares, New Issues	42,000	47,000	24,000
Stock Issued During Period, Shares, Dividend Reinvestment Plan	100,000	96,000	49,000