Revolving Credit Facility (Details) (USD $)			3 Months Ended					3 Months Ended				3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Revolving Credit Facility multiplier	Mar. 31, 2014 Revolving Credit Facility Minimum	Mar. 31, 2014 Revolving Credit Facility Maximum	Mar. 31, 2014 Revolving Credit Facility Prime rate	Mar. 31, 2013 Revolving Credit Facility Prime rate	Mar. 31, 2014 Revolving Credit Facility Prime rate Minimum	Mar. 31, 2014 Revolving Credit Facility Prime rate Maximum	Mar. 31, 2014 Revolving Credit Facility LIBOR	Mar. 31, 2013 Revolving Credit Facility LIBOR	Mar. 31, 2014 Revolving Credit Facility LIBOR Minimum	Mar. 31, 2014 Revolving Credit Facility LIBOR Maximum
Revolving credit facility
Revolving credit limit			$ 125,000,000
Potential future expansion of the Facility under accordion feature			175,000,000
Variable rate basis						Bank's prime rate plus a margin				LIBOR plus a margin
Interest rate margin per debt instrument (as a percent)								1.25%	2.25%			2.25%	3.25%
Actual interest rate margin (as a percent)						1.25%				2.50%
Weighted average interest rate (as a percent)						4.50%	4.50%			2.45%	2.54%
Quarterly commitment fee on the average daily unused facility balance (as a percent)				0.30%	0.50%
EBITDA multiplier			3.0
Percentage of acquired EBITDA which can be included in covenants calculation					50.00%
Borrowing capacity permitted to be used per formula			27,000,000
Irrevocable letters of credit outstanding			7,100,000
Remaining borrowing capacity available for use			19,900,000
Minimum net worth required to be maintained			161,300,000
Company's net worth	$ 215,485,000	$ 214,054,000