Segment Information (Segment Information) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 segments	Mar. 31, 2012
Segment Reporting Information [Line Items]
Number of reportable segments (in segments)	3
Revenues from external sources	$ 2,797,000,000	$ 2,830,400,000
Intersegment revenues	0	0
Segment pretax income (loss)	81,303,000	(13,561,000)
Western Region Operations [Member]
Segment Reporting Information [Line Items]
Revenues from external sources	2,662,500,000	2,649,000,000
Intersegment revenues	2,900,000	2,900,000
Segment pretax income (loss)	72,300,000	(8,800,000)
Government Contracts [Member]
Segment Reporting Information [Line Items]
Revenues from external sources	134,500,000	181,400,000
Intersegment revenues	0	0
Segment pretax income (loss)	9,000,000	22,000,000
Divested Operations and Services [Member]
Segment Reporting Information [Line Items]
Revenues from external sources	0	0
Intersegment revenues	0	0
Segment pretax income (loss)	0	(23,200,000)
Corporate/Other/Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues from external sources	0	0
Intersegment revenues	(2,900,000)	(2,900,000)
Segment pretax income (loss)	$ 0	$ (3,600,000)