Fair Value Measurements (Details Textual) (USD $)	6 Months Ended
	Jun. 30, 2012
Fair Value Measurements (Textual) [Abstract]
Percent of credit loss	3.30%
Rate of return required	5.00%
Estimated timeframe for auctions of securities minimum	3 years
Estimated timeframe for auctions of securities maximum	5 years
Percentage of liquidity risk premium	5.00%
Increase or decrease in the liquidity risk premium	1.00%
Increase or decrease, respectively, the fair value of the Failed Auction Securities	$ 400,000