Banking Facilities and Debt (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Summary of outstanding debt
Debt	$ 20,417,000		$ 21,667,000
Less current installments	5,000,000		5,000,000
Debt, excluding current installments	15,417,000		16,667,000
Interest rate swaps
Interest rate hedges
Interest rate swap liabilities	1,300,000		1,500,000
Interest rate swap liabilities included in accrued expenses	900,000		900,000
Interest rate swap liabilities included in other liabilities	400,000		600,000
Quarterly settlement payment pursuant to hedges	200,000	300,000
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
Quarterly principal payments	800,000
Final principal payment	10,000,000
Summary of outstanding debt
Debt	12,500,000		13,334,000
Term Loan | LIBOR | Interest rate swaps
Interest rate hedges
LIBOR (as a percent)	4.695%
Current interest rate (as a percent)	6.445%
Draw Term Loan
Banking facilities and other debt
Term	10 years
Face amount of term loan	20,000,000
Quarterly principal payments	400,000
Final principal payment	6,700,000
Summary of outstanding debt
Debt	7,917,000		8,337,000
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% 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%
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% 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%
Revolving Facility
Banking facilities and other debt
Maximum borrowing capacity	30,000,000
Letters of credit outstanding	$ 700,000
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%