Segment Information (Segment Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 segments	Sep. 30, 2012
Segment Reporting Information [Line Items]
Number of reportable segments (in segments)			3
Revenues	$ 2,775,031	$ 2,779,572	$ 8,310,499	$ 8,451,310
Segment pretax income (loss)	108,580	29,376	241,911	23,226
Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Western Region Operations [Member]
Segment Reporting Information [Line Items]
Revenues	2,625,700	2,596,900	7,886,700	7,898,200
Segment pretax income (loss)	85,200	20,200	204,300	12,600
Western Region Operations [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	2,700	2,700	8,400	8,300
Government Contracts [Member]
Segment Reporting Information [Line Items]
Revenues	149,300	169,800	423,800	527,400
Segment pretax income (loss)	23,500	21,100	50,600	66,600
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	12,900	0	25,700
Segment pretax income (loss)	0	(4,700)	0	(34,400)
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)	(100)	(7,200)	(13,000)	(21,600)
Corporate/Other/Eliminations [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	$ (2,700)	$ (2,700)	$ (8,400)	$ (8,300)