Segment Information (Segment Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 segments	Jun. 30, 2012
Segment Reporting Information [Line Items]
Number of reportable segments (in segments)			3
Revenues	$ 2,738,431	$ 2,841,339	$ 5,535,468	$ 5,671,738
Segment pretax income (loss)	52,028	7,411	133,331	(6,150)
Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Western Region Operations [Member]
Segment Reporting Information [Line Items]
Revenues	2,598,500	2,652,300	5,261,000	5,301,300
Segment pretax income (loss)	46,800	1,200	119,100	(7,600)
Western Region Operations [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	2,800	2,700	5,700	5,600
Government Contracts [Member]
Segment Reporting Information [Line Items]
Revenues	139,900	176,200	274,500	357,600
Segment pretax income (loss)	18,100	23,500	27,100	45,500
Government Contracts [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Divested Operations and Services [Member]
Segment Reporting Information [Line Items]
Revenues	0	12,800	0	12,800
Segment pretax income (loss)	0	(6,500)	0	(29,700)
Divested Operations and Services [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Corporate/Other/Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Segment pretax income (loss)	(12,900)	(10,800)	(12,900)	(14,400)
Corporate/Other/Eliminations [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	$ (2,800)	$ (2,700)	$ (5,700)	$ (5,600)