Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 participant	Dec. 31, 2013	Dec. 31, 2012
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	$ 17,500
Defined Contribution Plan, Employer Matching Contribution, Percent	6.00%
Defined Contribution Plan, Cost Recognized	5,000,000	4,100,000	2,800,000
Defined Contribution Plan, Employer Discretionary Contribution Amount		100,000
Number of Participants in Non Qualifed Deferred Compensation Plan	52
Deferred Compensation Liability, Current and Noncurrent	21,700,000	23,600,000
Multiemployer Plan, Period Contributions	29,422,000	27,165,000	22,723,000
Multiemployer Plans, Maximum Percent Funded Status for Red Zone	65.00%
Multiemployer Plans, Maximum Percent Funded Status for Yellow Zone and Minmum 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	3,043,000	3,260,000	2,368,000
Operating Engineers Pension Trust Fund [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	3,001,000	2,768,000	2,285,000
Pension Trust Fund for Operating Engineers Pension Plan [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	9,590,000	8,193,000	8,030,000
Laborers Pension Trust Fund for Northern California [Member] [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	2,682,000	2,500,000	2,320,000
Laborers Pension Fund [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	2,230,000	1,608,000	0
All Other Pension Trust Funds [Member]
Employee Benefits Plans [Line Items]
Multiemployer Plan, Period Contributions	$ 8,876,000	$ 8,836,000	$ 7,720,000