Accrued Workers' Compensation (Schedule Of Changes in Projected Benefit Obligations) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accrued Workers Compensation [Line Items]
Accumulated gain (loss)	$ (5,500,000)	$ 2,000,000
Workers' Compensation [Member]
Accrued Workers Compensation [Line Items]
Benefit obligations at January 1	17,412,000	9,702,000
Service cost	2,059,000	727,000	531,000
Interest cost	1,799,000	675,000	558,000
Actuarial loss	7,081,000	6,993,000
Benefit and administrative payments	(1,097,000)	(685,000)
Acquisition of ICG	26,930,000
Benefit obligations at December 31	54,184,000	17,412,000	9,702,000
Amortization of net gains (losses)	$ 1,100,000