Other borrowings (Details) (USD $)	12 Months Ended
	Dec. 31, 2012
Debt Instrument [Line Items]
Face amount	$ 25,000,000
Interest rate paid	3.00%
Frequency of periodic payment	quarterly
Quarterly principal payments	625,000
Date of first required payment	Sep. 30, 2012
Maturity date	Jun. 15, 2017
Minimum prepayment amount	100,000
Annual principal amortization	2,500,000
Fixed charge coverage ratio required, minimum (in hundredths)	125.00%
Debt issuance costs associated with Loan Agreement	$ 162,000
Amortization period of debt issuance costs	3 years
Minimum [Member]
Debt Instrument [Line Items]
Applicable margin (in hundredths)	2.25%
Maximum [Member]
Debt Instrument [Line Items]
Applicable margin (in hundredths)	3.00%
Base Rate [Member]
Debt Instrument [Line Items]
Description of interest rate terms	A base rate generally defined as the sum of (i) the highest of (x) the lender's "base" or "prime" rate, (y) the average overnight federal funds effective rate plus one-half percent (0.50%) per annum or (z) one-month LIBOR plus one percent (1%) per annum and (ii) an applicable margin as noted below; or
Applicable margin (in hundredths)	3.00%
LIBOR Rate [Member]
Debt Instrument [Line Items]
Description of interest rate terms	A LIBOR rate generally defined as the sum of (i) the average of the offered rates of interest quoted in the London Inter-Bank Eurodollar Market for U.S. Dollar deposits with prime banks (as published by Reuters or other commercially available source) for one, two or three months (all as selected by the Company), and (ii) an applicable margin.
Applicable margin (in hundredths)	3.00%
Preferred Stock [Member]
Debt Instrument [Line Items]
Number of shares of preferred stock redeemed with borrowings under Loan Agreement (in shares)	71,250