Stock Options - Exercise prices on options outstanding (Details 2) (USD $)					12 Months Ended			12 Months Ended			12 Months Ended			12 Months Ended			12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 Range of Exercise Prices $1.75 - $9.99	Dec. 31, 2011 Range of Exercise Prices $1.75 - $9.99	Dec. 31, 2010 Range of Exercise Prices $1.75 - $9.99	Dec. 31, 2012 Range of Exercise Prices $10.00 - $14.99	Dec. 31, 2011 Range of Exercise Prices $10.00 - $14.99	Dec. 31, 2010 Range of Exercise Prices $10.00 - $14.99	Dec. 31, 2012 Range of Exercise Prices $15.00 - $19.99	Dec. 31, 2011 Range of Exercise Prices $15.00 - $19.99	Dec. 31, 2010 Range of Exercise Prices $15.00 - $19.99	Dec. 31, 2012 Range of Exercise Prices $20.00 - $24.99	Dec. 31, 2011 Range of Exercise Prices $20.00 - $24.99	Dec. 31, 2010 Range of Exercise Prices $20.00 - $24.99	Dec. 31, 2012 Range of Exercise Prices $25.00 - $29.99	Dec. 31, 2011 Range of Exercise Prices $25.00 - $29.99	Dec. 31, 2010 Range of Exercise Prices $25.00 - $29.99	Dec. 31, 2012 Range of Exercise Prices $30.00 - $30.55	Dec. 31, 2011 Range of Exercise Prices $30.00 - $30.55	Dec. 31, 2010 Range of Exercise Prices $30.00 - $30.55
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding	173,888	167,983	175,485	174,220	17,158	22,861	46,245	111,410	120,802	108,180	24,620	3,620	120	12,800	12,800	12,800	2,500	2,500	2,740	5,400	5,400	5,400
Options lower range of exercise prices					$ 1.75			$ 10.00			$ 15.00			$ 20.00			$ 25.00			$ 30.00
Options upper range of exercise prices					$ 9.99			$ 14.99			$ 19.99			$ 24.99			$ 29.99			$ 30.55