Segment Information (Information About Industry Segments And Geographic Areas) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues from unrelated entities	$ 1,556,753,000	$ 1,590,035,000	$ 3,125,154,000	$ 3,128,556,000
Total revenues	1,556,753,000	1,590,035,000	3,125,154,000	3,128,556,000
Operating income (loss)	36,099,000	56,289,000	87,364,000	102,478,000
Restructuring expenses	(5,813,000)	0	(7,176,000)	0
Interest expense	(1,764,000)	(1,878,000)	(3,626,000)	(3,653,000)
Interest income	270,000	368,000	627,000	784,000
Income before income taxes	34,605,000	54,779,000	84,365,000	99,609,000
Total assets	3,105,336,000		3,105,336,000		3,107,070,000
Insurance recoveries			2,600,000
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(36,145,000)	(19,191,000)	(56,754,000)	(33,688,000)
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	(17,063,000)	(15,610,000)	(31,421,000)	(30,721,000)
Total assets	593,136,000		593,136,000		623,044,000
UNITED STATES
Segment Reporting Information [Line Items]
Revenues from unrelated entities	1,447,687,000	1,450,196,000	2,897,088,000	2,847,826,000
Total revenues	1,447,687,000	1,450,196,000	2,897,088,000	2,847,826,000
Operating income (loss)	63,512,000	67,937,000	129,219,000	125,755,000
Total assets	2,328,775,000		2,328,775,000		2,269,571,000
UNITED STATES | United States Electrical Construction And Facilities Services [Member]
Segment Reporting Information [Line Items]
Revenues from unrelated entities	336,330,000	295,846,000	643,914,000	586,383,000
UNITED STATES | United States Mechanical Construction And Facilities Services [Member]
Segment Reporting Information [Line Items]
Revenues from unrelated entities	583,963,000	626,617,000	1,125,080,000	1,200,820,000
UNITED STATES | United States Facilities Services [Member]
Segment Reporting Information [Line Items]
Revenues from unrelated entities	527,394,000	527,733,000	1,128,094,000	1,060,623,000
UNITED STATES | Operating Segments [Member] | United States Electrical Construction And Facilities Services [Member]
Segment Reporting Information [Line Items]
Total revenues	343,335,000	305,553,000	653,110,000	600,361,000
Operating income (loss)	25,236,000	22,409,000	44,176,000	45,975,000
Total assets	336,221,000		336,221,000		283,997,000
UNITED STATES | Operating Segments [Member] | United States Mechanical Construction And Facilities Services [Member]
Segment Reporting Information [Line Items]
Total revenues	598,847,000	631,850,000	1,150,631,000	1,209,416,000
Operating income (loss)	18,248,000	29,506,000	29,388,000	52,329,000
Total assets	821,900,000		821,900,000		785,286,000
UNITED STATES | Operating Segments [Member] | United States Facilities Services [Member]
Segment Reporting Information [Line Items]
Total revenues	541,650,000	531,984,000	1,150,101,000	1,071,737,000
Operating income (loss)	20,028,000	16,022,000	55,655,000	27,451,000
Total assets	1,170,654,000		1,170,654,000		1,200,288,000
UNITED KINGDOM | United Kingdom Construction And Facilities Services [Member]
Segment Reporting Information [Line Items]
Revenues from unrelated entities	109,066,000	139,839,000	228,066,000	280,730,000
UNITED KINGDOM | Operating Segments [Member] | United Kingdom Construction And Facilities Services [Member]
Segment Reporting Information [Line Items]
Total revenues	109,066,000	139,839,000	228,066,000	280,730,000
Operating income (loss)	(4,537,000)	3,962,000	(3,258,000)	7,444,000
Total assets	$ 183,425,000		$ 183,425,000		$ 214,455,000