Commitments And Contingencies (Narrative) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012 Customer Insurers LawSuits	Sep. 30, 2011	Sep. 30, 2012 Property acre Death Customer Insurers LawSuits	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010 California Wildfire Amador County [Member]	Sep. 30, 2012 California Wildfire San Diego [Member]	Dec. 31, 2010 California Wildfire San Diego [Member]
Commitments And Contingencies [Line Items]
Rent expense related to operating leases	$ 24,300,000	$ 30,900,000	$ 72,400,000	$ 86,100,000
Maximum guaranteed residual value	198,100,000		198,100,000
Estimated committed capital remainder of current year	10,100,000		10,100,000
Estimated committed capital in 2013	10,600,000		10,600,000
Purchase commitments related to operating equipment and vehicles for the remainder of 2012	7,800,000		7,800,000
Purchase commitments related to operating equipment and vehicles for 2013	11,500,000		11,500,000
Number of lawsuits related to California wildfire litigation	4		4
Amount of acreage damaged due to wildfire			198,000
Number of homes and structures damaged due to wildfire			1,500
Alleged deaths caused by wildfire			2
Alleged number of personal injuries caused by wildfire			Numerous
Loss Contingency, Settlement Agreement, Consideration	33,800,000		33,800,000
Expense under insurance previously recorded							7,500,000
Expenses funded by insurer							26,300,000
Liability recorded for fire claims						8,500,000		35,000,000
Amount sought by one insurer which reserves the right to contest coverage	25,000,000		25,000,000
Land damaged due to wildfire, in acres			16,800
Demand for payment of fire suppression costs	8,500,000		8,500,000
USDA intends to seek this amount	51,300,000		51,300,000
Amount of damages or penalties sought by USDA	59,800,000		59,800,000
Number of Insurers Participating Under a Reservation of Rights	2		2
Insurance recovery receivable						8,500,000
Damages Sought by Company in Arbitration, Value			16,500,000
Loss Contingency, Damages Sought by Customer in Arbitration counterclaim, Value			79,500,000
Number of customer represent ten percent or more of accounts receivable	1		1
Amount of billed and unbilled receivables accounted for by one customer	192,700,000		192,700,000
Amount of billed and unbilled receivables accounted for by one customer, percentage	11.40%		11.40%
Minimum percentage of billed and accounts receivable					10% or more
Minimum percentage of revenue	10% or more	10% or more	10% or more	10% or more
General liability insurance claims deductible	5,000,000	5,000,000
Auto liability insurance claims deductible	5,000,000	5,000,000
Worker's compensation claims per occurrence	5,000,000	5,000,000
Employer's liability claims subject to deductible per occurrence	1,000,000	1,000,000
Employee health care benefit plans subject to deductible per claimant	350,000	350,000
Gross amount accrued for insurance claims	189,000,000		189,000,000		201,200,000
Long-term insurance claims	143,600,000		143,600,000		155,400,000
Related insurance recoveries receivables	56,500,000		56,500,000		63,100,000
Related insurance recoveries/receivables included in prepaid expenses and other current assets	14,600,000		14,600,000		9,800,000
Related insurance recoveries receivables included in other assets net	41,900,000		41,900,000		53,300,000
Letters of credit issued under the credit facility	179,300,000		179,300,000
Total amount of outstanding performance bonds	2,050,000,000		2,050,000,000
Estimated cost to complete bonded projects	481,700,000		481,700,000
Partial withdrawal liability	32,600,000		32,600,000		32,600,000
Multiemployer Plan Withdrawal Obligation, amount suggested by Plan which is different than amount recorded by company	$ 39,700,000