Long-Term Debt (Details) (USD $)			6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Secured credit facility	Jun. 30, 2012 Secured credit facility Minimum	Jun. 30, 2012 Secured credit facility Maximum	Jun. 30, 2012 Secured credit facility March 31, 2013
Long-Term Debt
Maximum borrowing capacity under the credit facility			$ 60,000,000			$ 55,000,000
Amount outstanding under the credit facility	31,900,000	29,160,000	31,900,000
Interest rate at the end of the period (as a percent)			2.50%
Reference rate			LIBOR
Interest rate added to the reference rate (as a percent)			2.25%	2.00%	3.25%
Remaining maximum borrowings available pursuant to the credit facility			7,460,000
Amount to be borrowed to maintain compliance with the quarterly debt covenant calculation			$ 6,944,000