Segment Information (Segment Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 3,889,896	$ 3,038,935
Pretax income	67,709	61,960
Segment net income (loss)	29,988	28,787
Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Western Region Operations [Member]
Segment Reporting Information [Line Items]
Revenues	3,735,200	2,894,800
Pretax income	102,000	53,000
Segment net income (loss)	50,700	23,600
Western Region Operations [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	3,400	3,000
Government Contracts [Member]
Segment Reporting Information [Line Items]
Revenues	154,700	144,100
Pretax income	13,000	13,000
Segment net income (loss)	7,600	7,600
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
Pretax income	(47,300)	(4,000)
Segment net income (loss)	(28,300)	(2,400)
Corporate/Other/Eliminations [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	$ (3,400)	$ (3,000)