Segment Information (Segment Information) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 3,038,935,000	$ 2,797,037,000
Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Western Region Operations [Member]
Segment Reporting Information [Line Items]
Revenues	2,894,800,000	2,662,500,000
Segment pretax income (loss)	53,000,000	72,300,000
Western Region Operations [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	3,000,000	2,900,000
Government Contracts [Member]
Segment Reporting Information [Line Items]
Revenues	144,100,000	134,500,000
Segment pretax income (loss)	13,000,000	9,000,000
Government Contracts [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Corporate/Other/Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Segment pretax income (loss)	(4,000,000)	0
Corporate/Other/Eliminations [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	$ (3,000,000)	$ (2,900,000)