Stock Option Activity (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Arrangements with Employees and Nonemployees [Abstract]
Stock Option Vesting Period			4 years
Shares outstanding at beginning of period	2,370,085	2,974,613	2,621,686	3,331,031
Shares granted	10,000	69,500	167,000	183,400
Shares exercised	(87,730)	(257,570)	(291,820)	(543,014)
Shares forfeited or expired	(63,089)	(55,886)	(267,600)	(240,760)
Shares outstanding at end of period	2,229,266	2,730,657	2,229,266	2,730,657
Weighted average exercise price of options outstanding at beginning of period	$ 13.42	$ 12.48	$ 13.03	$ 11.91
Weighted average exercise price of options granted	$ 13.52	$ 17.19	$ 15.75	$ 17.18
Weighted average exercise price of options exercised	$ 6.59	$ 7.10	$ 6.91	$ 6.18
Weighted average exercise price of options forfeited or expired	$ 20.18	$ 17.13	$ 17.59	$ 16.42
Weighted average exercise price of options outstanding at end of period	$ 13.50	$ 13.01	$ 13.50	$ 13.01