Compensation Plans (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price (in dollars per share)	$ 33.03
Exercise price, minimum (in dollars per share)	$ 22.90
Exercise price, maximum (in dollars per share)	$ 41.74
Weighted average remaining contractual term	2 years 3 months 18 days
Aggregate intrinsic value	$ 319,930
Market price of common stock (in dollars per share)	$ 113.01
Directors Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)	4,000
Options granted	0	0