Long-term Debt and Line of Credit (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2013
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 34,300,000
Debt instrument, description of variable rate basis	Eurodollar
Line of credit facility, interest rate during period	2.40%
LIBOR
Debt Instrument [Line Items]
Line of credit facility, interest rate at period end		2.1875%
Secured Debt
Debt Instrument [Line Items]
Line of credit facility, additional borrowing capacity		25,000,000
Debt instrument, periodic payment, principal	389,000
Line of credit facility, minimum net worth		180,000,000
Line of credit facility, covenant terms, minimum net worth, incremental amount to base amount, % of current quarter consolidated net income	50.00%
Line of credit facility, covenant terms, minimum net worth, incremental amount to base amount, % of issuances of equity interests	75.00%
Line of credit facility, unused capacity commitment fee percentage	0.25%
Letter of credit | Secured Debt
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		20,000,000
Letters of credit outstanding, amount		742,000
Prime rate based Loans | Revolving Line of Credit [Member] | Secured Debt
Debt Instrument [Line Items]
Line of credit facility, integral multiple of borrowings	500,000
Prime rate based Loans | Swingline loan | Secured Debt
Debt Instrument [Line Items]
Line of credit facility, integral multiple of borrowings	100,000
Eurodollar Loans | Revolving Line of Credit [Member] | Secured Debt
Debt Instrument [Line Items]
Line of credit facility, integral multiple of borrowings	1,000,000
Eligible accounts receivable
Debt Instrument [Line Items]
Line of credit, current borrowing capacity base components	80.00%
Adjusted cash balance
Debt Instrument [Line Items]
Line of credit, current borrowing capacity base components	90.00%
Amended credit agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 35,000,000