Indebtedness (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Greater than or equal to 3.00 to 1.00
Credit Facilities
Consolidated leverage ratio, range	3.00
Less than 1.00 to 1.00
Credit Facilities
Consolidated leverage ratio, range	1.00
Minimum | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Consolidated leverage ratio	2.00
Minimum | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Consolidated leverage ratio	1.50
Minimum | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Consolidated leverage ratio	1.00
Maximum | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Consolidated leverage ratio	3.00
Maximum | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Consolidated leverage ratio	2.00
Maximum | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Consolidated leverage ratio	1.50
Alternate base rate | Greater than or equal to 3.00 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	1.00%
Alternate base rate | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	0.75%
Alternate base rate | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	0.50%
Alternate base rate | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	0.375%
Alternate base rate | Less than 1.00 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	0.25%
Reserve-adjusted LIBOR | Greater than or equal to 3.00 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	2.00%
Reserve-adjusted LIBOR | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	1.75%
Reserve-adjusted LIBOR | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	1.50%
Reserve-adjusted LIBOR | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	1.375%
Reserve-adjusted LIBOR | Less than 1.00 to 1.00
Credit Facilities
Basis spread on variable rate (as a percent)	1.25%
Letter of credit
Credit Facilities
Fronting fees (as a percent)	0.125%
Letter of credit | Greater than or equal to 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	2.00%
Letter of credit | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	1.75%
Letter of credit | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	1.50%
Letter of credit | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Commitment fee (as a percent)	1.375%
Letter of credit | Less than 1.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	1.25%
Senior credit facility
Credit Facilities
Maximum borrowing capacity under financing arrangement	2,075.0
Number of trailing fiscal quarters used in calculating the Consolidated Interest Coverage Ratio under senior credit facilities' covenants (in number of quarters)	4
Threshold amount of cash and cash equivalents above which amounts are netted against consolidated net debt for calculation of debt compliance	50.0
Number of trailing fiscal quarters used in calculating the Consolidated Leverage Coverage Ratio under senior credit facilities' covenants (in number of quarters)	4
Consolidated Leverage Ratio under senior credit facilities' covenants after certain permitted acquisitions	3.50
Maximum amount of capital stock repurchases and dividend declarations allowable (before adjustment) under senior credit facilities' covenants in any fiscal year if Consolidated Leverage Ratio is greater than or equal to 2.50 to 1.00	100.0
Consolidated leverage ratio greater than 2.50 to 1.00 - capital stock repurchases and dividend declarations used in calculation	300.0
Percentage of cumulative consolidated net income during the most recent fiscal quarter preceding stock repurchase or dividend declaration	50.00%
Percentage of consolidated net deficit removed from calculation of amounts available for stock repurchases and dividends	(100.00%)
Maximum amount of the commitments SPX can seek	1,000.0
Maximum Consolidated Senior Secured Leverage Ratio to seek additional commitments	2.75
Weighted-average interest rate of senior credit facilities (as a percent)	1.60%
Maximum period within which net proceeds should be reinvested	360 days
Security interest granted in capital stock of domestic subsidiaries or subsidiary guarantors (as a percent)	100.00%
Security interest granted in material first tier foreign subsidiaries (as a percent)	65.00%
Senior credit facility | Minimum
Credit Facilities
Consolidated Interest Coverage Ratio under senior credit facilities' covenants	3.50
Consolidated Leverage Ratio restricting amount of capital stock repurchases and dividend payments under senior credit facilities' covenants	2.50
Senior credit facility | Maximum
Credit Facilities
Consolidated Leverage Ratio under senior credit facilities' covenants	3.25
Maximum consolidated Leverage Ratio necessary for unlimited amount of capital stock repurchases and dividend payments under senior credit facilities' covenants	2.50
Senior credit facility | Alternate base rate
Credit Facilities
Description of variable rate (as a percent)	alternate base rate
Senior credit facility | Federal funds effective rate
Credit Facilities
Basis spread on variable rate (as a percent)	0.50%
Description of variable rate (as a percent)	federal funds effective rate
Senior credit facility | Prime rate
Credit Facilities
Description of variable rate (as a percent)	prime rate
Senior credit facility | One-Month LIBOR
Credit Facilities
Basis spread on variable rate (as a percent)	1.00%
Description of variable rate (as a percent)	one-month LIBOR
Senior credit facility | Reserve-adjusted LIBOR
Credit Facilities
Description of variable rate (as a percent)	reserve-adjusted LIBOR
Interest period which may be elected, shortest	1 month
Interest period which may be elected, second shortest	2 months
Interest period which may be elected, second longest	3 months
Interest period which may be elected, longest	6 months
Domestic and global revolving credit facilities
Credit Facilities
Amount of available borrowing capacity	313.2
Domestic and global revolving credit facilities | Letter of credit
Credit Facilities
Letters of credit issued, amount outstanding	53.8
Domestic revolving credit facility
Credit Facilities
Maximum borrowing capacity under financing arrangement	300.0
Domestic revolving credit facility | Greater than or equal to 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.35%
Domestic revolving credit facility | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.30%
Domestic revolving credit facility | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.275%
Domestic revolving credit facility | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.25%
Domestic revolving credit facility | Less than 1.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.225%
Global revolving credit facility
Credit Facilities
Maximum borrowing capacity under financing arrangement	200.0
Global revolving credit facility | Greater than or equal to 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.35%
Global revolving credit facility | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.30%
Global revolving credit facility | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.275%
Global revolving credit facility | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.25%
Global revolving credit facility | Less than 1.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.225%
Foreign credit instrument facility | Greater than or equal to 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	1.25%
Foreign credit instrument facility | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	1.00%
Foreign credit instrument facility | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.875%
Foreign credit instrument facility | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.80%
Foreign credit instrument facility | Less than 1.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.75%
Participation foreign credit instrument facility
Credit Facilities
Maximum borrowing capacity under financing arrangement	800.0
Fronting fees (as a percent)	0.25%
Term loan
Credit Facilities
Maximum borrowing capacity under financing arrangement	575.0
Foreign Credit Commitment
Credit Facilities
Amount of available borrowing capacity	304.7
Foreign Credit Commitment | Greater than or equal to 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.35%
Foreign Credit Commitment | Between 2.00 to 1.00 and 3.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.30%
Foreign Credit Commitment | Between 1.50 to 1.00 and 2.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.275%
Foreign Credit Commitment | Between 1.00 to 1.00 and 1.50 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.25%
Foreign Credit Commitment | Less than 1.00 to 1.00
Credit Facilities
Commitment fee (as a percent)	0.225%
Foreign Credit Commitment | Letter of credit
Credit Facilities
Letters of credit issued, amount outstanding	695.3
Bilateral foreign credit instrument facility
Credit Facilities
Maximum borrowing capacity under financing arrangement	200.0