Fair Value (Details) (USD $)	12 Months Ended				3 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Teradyne Inc.'s Diagnostic Solutions business ("DS")	Dec. 31, 2011 SPX Heat Transfer Inc.	Jul. 02, 2011 SPX Heat Transfer Inc.	Dec. 31, 2011 SPX Heat Transfer Inc.	Dec. 31, 2009 Service Solutions	Dec. 31, 2011 Industrial Products and Services	Dec. 31, 2011 Thermal Equipment and Services	Dec. 31, 2010 Thermal Equipment and Services	Dec. 31, 2009 Thermal Equipment and Services	Dec. 31, 2011 Test and Measurement	Dec. 31, 2010 Test and Measurement	Dec. 31, 2009 Test and Measurement	Dec. 31, 2011 Quoted Prices in Active Markets for Identical Assets (Level 1) Noncurrent assets - Investment in equity securities and available-for-sale securities	Dec. 31, 2010 Quoted Prices in Active Markets for Identical Assets (Level 1) Noncurrent assets - Investment in equity securities and available-for-sale securities	Dec. 31, 2011 Significant Observable Inputs (Level 2) Current assets - FX embedded derivatives, FX forward contracts and commodity contracts	Dec. 31, 2010 Significant Observable Inputs (Level 2) Current assets - FX embedded derivatives, FX forward contracts and commodity contracts	Dec. 31, 2011 Significant Observable Inputs (Level 2) Current liabilities - FX forward contracts and FX embedded derivatives	Dec. 31, 2010 Significant Observable Inputs (Level 2) Current liabilities - FX forward contracts and FX embedded derivatives	Dec. 31, 2011 Significant Observable Inputs (Level 2) Long-term liabilities - FX embedded derivatives	Dec. 31, 2010 Significant Observable Inputs (Level 2) Long-term liabilities - FX embedded derivatives	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) Noncurrent assets - Investment in equity securities and available-for-sale securities	Dec. 31, 2010 Significant Unobservable Inputs (Level 3) Noncurrent assets - Investment in equity securities and available-for-sale securities
Assets and liabilities measured at fair value on a recurring basis
Certain investments in equity securities that are not readily marketable, fair value																								$ 7,800,000	$ 8,500,000
Fair value of derivative liability																				1,900,000	6,100,000	14,800,000	33,200,000
Goodwill, Impairment Loss	20,800,000				3,600,000	17,200,000	20,800,000	187,700,000		20,800,000
Indefinite-lived intangible assets impairment loss						7,500,000						6,100,000
Fair value of derivative assets																5,200,000	12,800,000	1,200,000	4,100,000
Fair value of assets after impairment, held by a business			8,900,000						0
Impairment charges to write off the net book value of assets in connection with the closing of a facility	6,500,000
Fair value of assets after impairment, in connection with the closing of a facility									0
Equity in consolidated joint venture									0
Reconciliation of investment in equity securities measured at fair value using significant unobservable inputs
Balance at beginning of year	8,500,000
Purchases		9,800,000
Losses included in earnings	(700,000)	(1,300,000)
Balance at end of year	7,800,000	8,500,000
Fair value of assets and liabilities
Special charges relating to asset impairments	12,100,000	7,900,000	11,100,000	3,700,000		24,700,000					4,000,000	5,500,000	3,900,000	1,600,000	2,800,000
Impairment charges								1,000,000	800,000	7,500,000
Fair value of asset	16,200,000	4,700,000
Fair value of debt instruments	2,099,100,000
Carrying value of debt instruments	2,001,100,000
Pre-tax impairment charges recorded to Gain (loss) on disposition of discontinued operations, net of tax			$ 20,800,000