Banking Facilities and Debt (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Summary of outstanding debt
Debt	$ 22,917,000		$ 22,917,000		$ 26,667,000
Less current installments	5,000,000		5,000,000		5,000,000
Debt, excluding current installments	17,917,000		17,917,000		21,667,000
Interest rate swaps
Interest rate hedges
Interest rate swap liabilities	1,800,000		1,800,000		2,600,000
Interest rate swap liabilities included in accrued expenses	1,000,000		1,000,000		1,100,000
Interest rate swap liabilities included in other liabilities	800,000		800,000		1,500,000
Quarterly settlement payment pursuant to hedges	300,000	300,000	900,000	1,000,000
LIBOR
Banking facilities and other debt
Interest rate basis			LIBOR
Lender's prime rate
Banking facilities and other debt
Interest rate basis			Lender's Prime Rate
Minimum | LIBOR
Banking facilities and other debt
Interest rate margin (as a percent)			1.75%
Minimum | Lender's prime rate
Banking facilities and other debt
Interest rate margin (as a percent)			0.00%
Maximum | LIBOR
Banking facilities and other debt
Interest rate margin (as a percent)			2.75%
Maximum | Lender's prime rate
Banking facilities and other debt
Interest rate margin (as a percent)			1.00%
Term Loan
Banking facilities and other debt
Term			10 years
Face amount of term loan	40,000,000		40,000,000
Quarterly principal payments			800,000
Final principal payment			10,000,000
Summary of outstanding debt
Debt	14,167,000		14,167,000		16,667,000
Term Loan | LIBOR | Interest rate swaps
Interest rate hedges
LIBOR (as a percent)			4.695%
Current interest rate (as a percent)	6.445%		6.445%
Draw Term Loan
Banking facilities and other debt
Term			10 years
Face amount of term loan	20,000,000		20,000,000
Quarterly principal payments			400,000
Final principal payment			6,700,000
Summary of outstanding debt
Debt	8,750,000		8,750,000		10,000,000
75% of the outstanding balance of the Draw Term Loan | Interest rate swaps
Interest rate hedges
Percentage of outstanding balance of debt hedged	75.00%		75.00%
75% of the outstanding balance of the Draw Term Loan | LIBOR | Interest rate swaps
Interest rate hedges
LIBOR (as a percent)			4.875%
Current interest rate (as a percent)	6.625%		6.625%
25% of the outstanding balance of the Draw Term Loan | Interest rate swaps
Interest rate hedges
Percentage of outstanding balance of debt hedged	25.00%		25.00%
25% of the outstanding balance of the Draw Term Loan | LIBOR | Interest rate swaps
Interest rate hedges
LIBOR (as a percent)			5.50%
Current interest rate (as a percent)	7.25%		7.25%
Revolving Facility
Banking facilities and other debt
Maximum borrowing capacity	30,000,000		30,000,000
Letters of credit outstanding	$ 600,000		$ 600,000		$ 637,000
Revolving Facility | Minimum
Banking facilities and other debt
Commitment fee (as a percent)			0.25%
Revolving Facility | Maximum
Banking facilities and other debt
Commitment fee (as a percent)			0.40%