Stock Option Plans (Details 4) (Officer and Employee Plans [Member], USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Officer and Employee Plans [Member]
Shares, Outstanding	572,600		520,900	799,675
Shares, Granted	202,000		221,000	0
Shares, Exercised	0		0	0
Shares, Forfeited	(104,300)		(169,300)	(278,775)
Shares, Outstanding	670,300		572,600	520,900
Shares, Options exercisable	274,680		295,415	385,270
Weighted-average fair value of options granted during the year	$ 0.78		$ 0.95	$ 0
Average Exercisable Price Outstanding (in dollars per share)	$ 4.63		$ 5.79	$ 6.18
Average Exercisable Price Granted (in dollars per share)	$ 1.65		$ 1.67	$ 0
Average Exercisable Price Exercised (in dollars per share)	$ 0		$ 0	$ 0
Average Exercisable Price Forfeited (in dollars per share)	$ 3.89		$ 4.31	$ 6.90
Average Exercisable Price Outstanding (in dollars per share)	$ 3.86		$ 4.63	$ 5.79
Average Exercisable Price, Options exercisable (in dollars per share)	$ 6.82		$ 6.67	$ 5.88
Aggregate Intrinsic Value Outstanding	$ 232,900	[1]
Aggregate Intrinsic Value Options exercisable at year end	$ 0	[1]

[1] The aggregate intrinsic value of a stock option in the table above represents the total pre-tax intrinsic value (the amount by which the current market value of the underlying stock exceeds the exercise price of the option) that would have been received by the option holders had all option holders exercised their options on December 31, 2012. This amount changes based on changes in the market value of Cornerstone's stock.