Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 participant	Dec. 31, 2010	Dec. 31, 2009
Employee Benefits Plans [Line Items]
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	50.00%
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Dollar Amount	$ 16,500
Defined Contribution Plan, Employer Matching Contribution, Percent	6.00%
Defined Contribution Plan, Cost Recognized	300,000	9,000,000	9,900,000
Number of Participants in Non Qualifed Deferred Compensation Plan	61
Deferred Compensation Liability, Current and Noncurrent	25,000,000	28,400,000
Multiemployer Plan, Period Contributions	21,969,000	20,317,000	20,215,000
Multiemployer Plans, Maximum Percent Funded Status for Red Zone	65.00%
Multiemployer Plans, Maxium Percent Funded Status for Yellow and Orange Zone and Minimum Percent for Green Zone	80.00%
Locals 302 and 612 Operating Engineers Employers Retirement Fund [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	2,386,000	2,040,000	2,103,000
Operating Engineers Pension Trust Fund [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	2,099,000	2,127,000	2,529,000
Pension Trust Fund for Operating Engineers Pension Plan [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	7,296,000	6,394,000	6,974,000
All Other Pension Trust Funds [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	$ 10,188,000	$ 9,756,000	$ 8,609,000