Banking Facilities and Debt (Details) (USD $)	3 Months Ended			3 Months Ended			3 Months Ended						0 Months Ended	3 Months Ended		3 Months Ended				3 Months Ended		3 Months Ended			3 Months Ended
	Mar. 31, 2012	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Interest rate swaps	Mar. 31, 2012 Interest rate swaps	Dec. 31, 2012 Interest rate swaps	Mar. 31, 2013 LIBOR	Mar. 31, 2013 Lender's prime rate	Mar. 31, 2013 Minimum LIBOR	Mar. 31, 2013 Minimum Lender's prime rate	Mar. 31, 2013 Maximum LIBOR	Mar. 31, 2013 Maximum Lender's prime rate	Apr. 01, 2013 Term Loan	Mar. 31, 2013 Term Loan	Dec. 31, 2012 Term Loan	Mar. 31, 2013 Term Loan LIBOR Interest rate swaps	Mar. 31, 2013 Draw Term Loan	Dec. 31, 2012 Draw Term Loan	Mar. 31, 2013 75% of the outstanding balance of the Draw Term Loan Interest rate swaps	Mar. 31, 2013 75% of the outstanding balance of the Draw Term Loan LIBOR Interest rate swaps	Mar. 31, 2013 25% of the outstanding balance of the Draw Term Loan Interest rate swaps	Mar. 31, 2013 25% of the outstanding balance of the Draw Term Loan LIBOR Interest rate swaps	Mar. 31, 2013 Revolving Facility	Dec. 31, 2012 Revolving Facility	Mar. 31, 2013 Revolving Facility Minimum	Mar. 31, 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				2,300,000		2,600,000
Interest rate swap liabilities included in accrued expenses				1,100,000		1,100,000
Interest rate swap liabilities included in other liabilities				1,300,000		1,500,000
Quarterly settlement payment pursuant to hedges				294,000	339,000
Summary of outstanding debt
Debt		26,667,000	26,667,000											16,667,000	16,667,000		10,000,000	10,000,000
Less current installments		6,250,000	5,000,000
Debt, excluding current installments		20,417,000	21,667,000
Repayment of debt	$ 1,250,000												$ 1,250,000