Banking Facilities and Debt (Details) (USD $)	6 Months Ended			3 Months Ended		6 Months Ended			6 Months Ended						0 Months Ended	6 Months Ended		6 Months Ended				6 Months Ended		6 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Interest rate swaps	Jun. 30, 2012 Interest rate swaps	Jun. 30, 2013 Interest rate swaps	Jun. 30, 2012 Interest rate swaps	Dec. 31, 2012 Interest rate swaps	Jun. 30, 2013 LIBOR	Jun. 30, 2013 Lender's prime rate	Jun. 30, 2013 Minimum LIBOR	Jun. 30, 2013 Minimum Lender's prime rate	Jun. 30, 2013 Maximum LIBOR	Jun. 30, 2013 Maximum Lender's prime rate	Jul. 01, 2013 Term Loan	Jun. 30, 2013 Term Loan	Dec. 31, 2012 Term Loan	Jun. 30, 2013 Term Loan LIBOR Interest rate swaps	Jun. 30, 2013 Draw Term Loan	Dec. 31, 2012 Draw Term Loan	Jun. 30, 2013 75% of the outstanding balance of the Draw Term Loan Interest rate swaps	Jun. 30, 2013 75% of the outstanding balance of the Draw Term Loan LIBOR Interest rate swaps	Jun. 30, 2013 25% of the outstanding balance of the Draw Term Loan Interest rate swaps	Jun. 30, 2013 25% of the outstanding balance of the Draw Term Loan LIBOR Interest rate swaps	Jun. 30, 2013 Revolving Facility	Dec. 31, 2012 Revolving Facility	Jun. 30, 2013 Revolving Facility Minimum	Jun. 30, 2013 Revolving Facility Maximum
Banking facilities and other debt
Term																10 years			10 years
Face amount of term loan																$ 40,000,000			$ 20,000,000
Maximum borrowing capacity																									30,000,000
Letters of credit outstanding																									637,000	637,000
Quarterly principal payments																833,000			417,000
Final principal payment																10,000,000			6,700,000
Commitment fee (as a percent)																											0.25%	0.40%
Interest rate basis									LIBOR	Lender's Prime Rate
Interest rate margin (as a percent)											1.75%	0.00%	2.75%	1.00%
Interest rate hedges
LIBOR (as a percent)																		4.695%				4.875%		5.50%
Percentage of outstanding balance of debt hedged																					75.00%		25.00%
Current interest rate (as a percent)																		6.445%				6.625%		7.25%
Interest rate swap liabilities				2,000,000		2,000,000		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				1,000,000		1,000,000		1,500,000
Quarterly settlement payment pursuant to hedges				292,000	335,000	586,000	674,000
Summary of outstanding debt
Debt	25,417,000		26,667,000													15,833,000	16,667,000		9,584,000	10,000,000
Less current installments	6,250,000		5,000,000
Debt, excluding current installments	19,167,000		21,667,000
Repayment of debt	$ 1,250,000	$ 2,500,000													$ 1,250,000