Retirement Plans - Schedule of Multiemployer Plans (Details) - Multiemployer Plan, Plan Information, Available - Domestic - Multiemployer Plans, Pension - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Multiemployer Plans [Line Items]
Contributions	$ 167,297	$ 147,056	$ 137,991
Plumbers & Pipefitters National Pension Fund
Multiemployer Plans [Line Items]
EIN	526152779
Pension Plan Number	001
PPA Zone Status	Yellow	Yellow
FIP/RP Status	Implemented
Contributions	$ 12,034	$ 12,021	10,425
Sheet Metal Workers National Pension Fund
Multiemployer Plans [Line Items]
EIN	526112463
Pension Plan Number	001
PPA Zone Status	Yellow	Yellow
FIP/RP Status	Implemented
Contributions	$ 11,280	$ 10,891	9,977
Northern California Pipe Trades Pension Plan
Multiemployer Plans [Line Items]
EIN	526054620
Pension Plan Number	001
PPA Zone Status	Red	Red
FIP/RP Status	Implemented
Contributions	$ 11,075	$ 6,697	6,000
National Electrical Benefit Fund
Multiemployer Plans [Line Items]
EIN	530181657
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 10,328	$ 8,513	7,985
Pension, Hospitalization & Benefit Plan of the Electrical Industry- Pension Trust Account
Multiemployer Plans [Line Items]
EIN	136123601
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 9,687	$ 7,543	6,219
NECA-IBEW Pension Trust Fund
Multiemployer Plans [Line Items]
EIN	943190386
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 6,495	$ 3,544	3,270
Central Pension Fund of the IUOE & Participating Employers
Multiemployer Plans [Line Items]
EIN	366052390
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 6,211	$ 6,465	6,518
Electrical Contractors Association of the City of Chicago Local Union 134, IBEW Joint Pension Trust of Chicago Pension Plan 2
Multiemployer Plans [Line Items]
EIN	516030753
Pension Plan Number	002
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 5,518	$ 5,759	4,051
Plumbers Pipefitters & Mechanical Equipment Service Local Union 392 Pension Plan
Multiemployer Plans [Line Items]
EIN	310655223
Pension Plan Number	001
PPA Zone Status	Red	Red
FIP/RP Status	Implemented
Contributions	$ 5,202	$ 5,554	4,962
Sheet Metal Workers Pension Plan of Northern California
Multiemployer Plans [Line Items]
EIN	516115939
Pension Plan Number	001
PPA Zone Status	Red	Red
FIP/RP Status	Implemented
Contributions	$ 5,164	$ 4,851	3,467
Southern California Pipe Trades Retirement Fund
Multiemployer Plans [Line Items]
EIN	516108443
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 4,371	$ 2,743	2,863
Pipefitters Union Local 537 Pension Fund
Multiemployer Plans [Line Items]
EIN	516030859
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 3,970	$ 3,939	2,981
NECA-IBEW Pension Trust Fund
Multiemployer Plans [Line Items]
EIN	516029903
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 3,752	$ 1,498	1,287
Eighth District Electrical Pension Fund
Multiemployer Plans [Line Items]
EIN	846100393
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 3,444	$ 3,411	2,695
Electrical Workers Local No. 26 Pension Trust Fund
Multiemployer Plans [Line Items]
EIN	526117919
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 3,390	$ 2,620	2,880
Southern California IBEW-NECA Pension Trust Fund
Multiemployer Plans [Line Items]
EIN	956392774
Pension Plan Number	001
PPA Zone Status	Red	Orange
FIP/RP Status	Implemented
Contributions	$ 3,289	$ 2,894	2,776
U.A. Plumbers Local 24 Pension Fund
Multiemployer Plans [Line Items]
EIN	226042823
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 3,147	$ 2,431	1,998
Sheet Metal Workers Pension Plan of Southern California, Arizona & Nevada
Multiemployer Plans [Line Items]
EIN	956052257
Pension Plan Number	001
PPA Zone Status	Yellow	Red
FIP/RP Status	Pending
Contributions	$ 2,946	$ 2,310	1,824
U.A. Local 393 Pension Trust Fund Defined Benefit
Multiemployer Plans [Line Items]
EIN	946359772
Pension Plan Number	002
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 2,490	$ 4,597	3,585
Heating, Piping & Refrigeration Pension Fund
Multiemployer Plans [Line Items]
EIN	521058013
Pension Plan Number	001
PPA Zone Status	Green	Green
FIP/RP Status	NA
Contributions	$ 2,402	$ 1,948	1,877
San Diego Electrical Pension Plan
Multiemployer Plans [Line Items]
EIN	956101801
Pension Plan Number	001
PPA Zone Status	Green	Red
FIP/RP Status	NA
Contributions	$ 2,216	$ 2,109	1,878
Boilermaker-Blacksmith National Pension Trust
Multiemployer Plans [Line Items]
EIN	486168020
Pension Plan Number	001
PPA Zone Status	Yellow	Yellow
FIP/RP Status	Implemented
Contributions	$ 1,710	$ 1,367	1,177
U.A. Local 38 Defined Benefit Pension Plan
Multiemployer Plans [Line Items]
EIN	941285319
Pension Plan Number	001
PPA Zone Status	Yellow	Yellow
FIP/RP Status	Implemented
Contributions	$ 1,521	$ 1,526	1,605
Plumbing & Pipe Fitting Local 219 Pension Fund
Multiemployer Plans [Line Items]
EIN	346682376
Pension Plan Number	001
PPA Zone Status	Red	Red
FIP/RP Status	Implemented
Contributions	$ 838	$ 1,262	1,107
Plumbers & Pipefitters Local Union No. 502 & 633 Pension Fund
Multiemployer Plans [Line Items]
EIN	616078145
Pension Plan Number	001
PPA Zone Status	Red	Red
FIP/RP Status	Implemented
Contributions	$ 713	$ 365	232
Steamfitters Local Union No. 420 Pension Plan
Multiemployer Plans [Line Items]
EIN	232004424
Pension Plan Number	001
PPA Zone Status	Red	Red
FIP/RP Status	Implemented
Contributions	$ 709	$ 845	862
Carpenters Pension Trust Fund for Northern California
Multiemployer Plans [Line Items]
EIN	946050970
Pension Plan Number	001
PPA Zone Status	Red	Red
FIP/RP Status	Implemented
Contributions	$ 584	$ 380	522
Other Multiemployer Pension Plans
Multiemployer Plans [Line Items]
Contributions	$ 42,811	$ 38,973	$ 42,968

The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12b
-Subsection 1

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- Definition

Three digit plan number for a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

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- Definition

Amount of contributions made to multiemployer plans by the employer. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450702-114947

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450691-114947

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (e)(1)
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- Definition

Indicate the multiemployer plan's certified zone status as currently required by the Pension Protection Act of 2006 or a subsequent amendment thereof. The zone status categories are red (critical status), orange (seriously endangered), yellow (endangered), and green (none of the above). The acceptable values are "red", "orange", "yellow", "green", "other", and "NA". A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

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- Definition

Indicate whether a funding improvement plan or rehabilitation plan has been implemented or is pending for a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. The acceptable values are "no", "pending", "implemented", "other", and "NA".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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