Long-Term Debt Obligations (Details 3) (USD $)	3 Months Ended								12 Months Ended									12 Months Ended										12 Months Ended							12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Revolving credit facility item	Sep. 23, 2011 Revolving credit facility	Dec. 31, 2012 Revolving credit facility Through December 31, 2013	Dec. 31, 2012 Revolving credit facility Through June 30, 2014	Dec. 31, 2012 Revolving credit facility Through maturity	Dec. 31, 2012 Revolving credit facility Actual	Dec. 31, 2012 Revolving credit facility Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: Less than 0.75	Dec. 31, 2012 Revolving credit facility Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 0.75 to 1.25	Dec. 31, 2012 Revolving credit facility Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.25 to 2.00	Dec. 31, 2012 Revolving credit facility Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA:2.00 to 2.50	Dec. 31, 2012 Revolving credit facility Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA:2.50 or greater	Dec. 31, 2012 Revolving credit facility Minimum Covenant Requirement	Dec. 31, 2012 Revolving credit facility Maximum	Dec. 31, 2012 Revolving credit facility Maximum Covenant Requirement Through December 31, 2013	Dec. 31, 2012 Revolving credit facility Maximum Covenant Requirement Through June 30, 2014	Dec. 31, 2012 Revolving credit facility Maximum Covenant Requirement Through maturity	Dec. 31, 2012 Revolving credit facility Base rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: Less than 0.75	Dec. 31, 2012 Revolving credit facility Base rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 0.75 to 1.25	Dec. 31, 2012 Revolving credit facility Base rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.25 to 2.00	Dec. 31, 2012 Revolving credit facility Base rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA:2.00 to 2.50	Dec. 31, 2012 Revolving credit facility Base rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA:2.50 or greater	Dec. 31, 2012 Revolving credit facility Base rate Federal Funds Rate	Dec. 31, 2012 Revolving credit facility Base rate Wells Fargo Bank, N.A. Prime Rate	Dec. 31, 2012 Revolving credit facility Base rate One-month LIBOR	Dec. 31, 2012 Revolving credit facility Base rate Six-month LIBOR	Dec. 31, 2012 Revolving credit facility Eurodollar rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: Less than 0.75	Dec. 31, 2012 Revolving credit facility Eurodollar rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 0.75 to 1.25	Dec. 31, 2012 Revolving credit facility Eurodollar rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.25 to 2.00	Dec. 31, 2012 Revolving credit facility Eurodollar rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA:2.00 to 2.50	Dec. 31, 2012 Revolving credit facility Eurodollar rate Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA:2.50 or greater	Dec. 31, 2012 Revolving credit facility Eurodollar rate One-month LIBOR	Dec. 31, 2012 Revolving credit facility Eurodollar rate Six-month LIBOR
Long-Term Debt Obligations
Borrowing capacity													$ 125,000,000
Letters of credit amount outstanding												48,200,000
Credit available												76,800,000
Book value of assets pledged as collateral												74,200,000
Reconciliation of Credit Facility Adjusted EBITDA to net income
Net income (loss) including noncontrolling interests	5,145,000	5,325,000	4,047,000	(2,668,000)	2,085,000	(36,569,000)	3,162,000	(5,170,000)	11,849,000	(36,492,000)	14,740,000	11,849,000
Income taxes - continuing operations									10,045,000	(5,463,000)	11,193,000	10,045,000
Interest expense, net												1,571,000
Depreciation and amortization expense												20,630,000
Stock compensation expense									2,800,000	3,600,000	3,700,000	2,797,000
Income taxes - discontinued operation												212,000
EBITDA attributable to noncontrolling interests												275,000
Pre-acquisition results of acquired companies, as defined in the credit agreement												730,000
Credit Facility Adjusted EBITDA												48,109,000
Principal financial covenants
Leverage ratio												0.15		3.00	2.75	2.50
Net leverage ratio used to determine exclusion of stock repurchases and the payment of dividends for calculation of the fixed charge coverage ratio																									2.00	1.50	1.00
Fixed charge coverage ratio																	16.31
Permitted amount of acquisitions per transaction												15,000,000
Period prior to acquisition for which aggregate purchase price is considered for determining permitted amount of acquisitions per transaction												12 months
Aggregate purchase price of current acquisition and acquisitions in the preceding 12 month period for determining permitted amount of acquisition per transaction																								30,000,000
Net leverage ratio used as basis for other restrictions																							2.00
Number of interest rate options												2
Period of Credit Facility Adjusted EBITDA for determining additional margins												12 months
Market rates relating to interest options
Variable rate basis																												Base rate	Base rate	Base rate	Base rate	Base rate			One-month LIBOR	Six-month LIBOR	Eurodollar rate	Eurodollar rate	Eurodollar rate	Eurodollar rate	Eurodollar rate
Interest rate margin (as a percent)																												0.75%	1.00%	1.25%	1.50%	1.75%	0.50%		1.00%		1.75%	2.00%	2.25%	2.50%	2.75%
Market rate (as a percent)																																	0.67%	3.25%	1.21%							0.21%	0.51%
Additional per annum interest margin added under:
Variable rate basis																												Base rate	Base rate	Base rate	Base rate	Base rate			One-month LIBOR	Six-month LIBOR	Eurodollar rate	Eurodollar rate	Eurodollar rate	Eurodollar rate	Eurodollar rate
Additional per annum interest margin (as a percent)																												0.75%	1.00%	1.25%	1.50%	1.75%	0.50%		1.00%		1.75%	2.00%	2.25%	2.50%	2.75%
Letter of credit fees (as a percent)																		1.30%	1.50%	1.70%	1.90%	2.10%
Commitment fees on any portion of the Revolving Loan capacity not in use for borrowings or letters of credit at any given time (as a percent)																		0.25%	0.30%	0.35%	0.45%	0.50%
Estimated interest rate (as a percent)												2.30%
Financing and professional cost												$ 500,000