Common Stock (Details) (USD $)	12 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2013	Feb. 15, 2008 Employee benefit stock	Dec. 31, 2013 Common Stock	Dec. 31, 2013 Stock Options	Dec. 31, 2012 Stock Options	Dec. 31, 2011 Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Common share purchase right dividend (in shares)		1
Number of common shares each right is entitled to (in shares)		1
Common share purchase right exercise price (in dolalrs per share)		200.00
Stock repurchase program, authorized amount			$ 30,000,000.0
Share repurchase program period in force (in years)			2 years
Shares repurchased during the period (shares)	888,056
Antidilutive stock options excluded from computation of earnings per share (in shares)				23,258	60,400	137,720