Basis of Presentation of Interim Period Statements (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Amount retained by company per occurrence	$ 5,000,000
Basis of Presentation of Interim Period Statements (Additional Textual) [Abstract]
Minimum term of revenue contract	1 year
Notice period to cancel or terminate revenue contract	30 days
Allowance for doubtful accounts	363,000		452,000
Workers' compensation liability	61,600,000	55,765,000	51,200,000	43,335,000	40,996,000	39,301,000
Insured claims	858,000		1,900,000
Estimate of liability for unpaid safety incentives	8,700,000		6,300,000
Maximum [Member]
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Workers' compensation insurance coverage	15,000,000
Minimum [Member]
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Workers' compensation insurance coverage	5,000,000
Maryland [Member]
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Amount retained by company per occurrence	1,000,000
Maryland [Member] \| Maximum [Member]
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Workers' compensation insurance coverage	25,000,000
Maryland [Member] \| Minimum [Member]
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Workers' compensation insurance coverage	1,000,000
Colorado [Member]
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Amount retained by company per occurrence	500,000
Colorado [Member] \| Maximum [Member]
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Workers' compensation insurance coverage	Statutory limits per occurrence
Colorado [Member] \| Minimum [Member]
Basis of Presentation of Interim Period Statements (Textual) [Abstract]
Workers' compensation insurance coverage	$ 500,000