The maximum period over which the fair value of restricted stock and restricted stock units are amortized.

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The historical period upon which annual expected stock price volatility is based.

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Represents the daily treasury yield curve period, in years, upon which the average risk-free interest rate is based.

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Represents the assumed correlation between the total shareholder return for the entities stock and the S&P 500 Composite Index and the S&P Composite 1500 Industrials Index.

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Represents the amount by which common stock available is reduced for each share granted.

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Represents the percentage of the target award, which each participant can earn under the plan.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Amount of cash inflow from realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Number of options outstanding, including both vested and non-vested options.

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An excess of the fair value of the modified award over the fair value of the award immediately before the modification.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Shareholders' Equity and Stock-Based Compensation (Details 3) $ in Millions						12 Months Ended
	Oct. 14, 2015	Jan. 02, 2015	Jan. 02, 2014	Apr. 01, 2013	Jan. 02, 2013	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)
Stock-based Compensation
Classification of excess tax benefits from stock-based compensation as financing cash flows \| $						$ 0.8	$ 9.7	$ 6.3
Maximum period over which the fair value of restricted stock shares and restricted stock units are amortized						3 years
Assumptions in determining the fair value of awards granted
Historical period upon which annual expected stock price volatility is based						3 years
2002 Stock Compensation Plan
Stock-based Compensation
Shares available for grant \| shares						443,000
Reduction of shares available for grant \| shares						2
Directors' Plan
Stock-based Compensation
Shares available for grant \| shares						27,000.000
Minimum
Assumptions in determining the fair value of awards granted
Daily treasury yield curve period upon which average risk-free interest rate is based						1 year
Maximum
Assumptions in determining the fair value of awards granted
Daily treasury yield curve period upon which average risk-free interest rate is based						3 years
Restricted stock shares and restricted stock units
Stock-based Compensation
Compensation expense \| $						$ 34.5	33.1	26.5
Related tax benefit \| $						$ 13.1	$ 12.6	$ 10.1
Assumptions in determining the fair value of awards granted
Annual expected stock price volatility (as a percent)			33.70%	35.50%	36.30%
Annual expected dividend yield (as a percent)			1.02%	1.29%	1.42%
Risk-free interest rate (as a percent)			0.76%	0.33%	0.37%
Correlation between total shareholder return for SPX and the applicable S&P index			0.7631	0.7668	0.7778
Restricted stock shares and restricted stock units \| Directors' Plan
Stock-based Compensation
Vesting period						1 year	1 year	1 year
Restricted stock shares and restricted stock units \| S&P Composite 1500 Industrials Index
Assumptions in determining the fair value of awards granted
Annual expected stock price volatility (as a percent)			19.90%	21.20%	22.40%
Risk-free interest rate (as a percent)			0.76%	0.33%	0.37%
Restricted stock shares and restricted stock units \| Minimum
Stock-based Compensation
Vesting period						1 year
Restricted stock shares and restricted stock units \| Maximum
Stock-based Compensation
Vesting period						3 years
Target performance awards
Stock-based Compensation
Vesting period							3 years
Target performance awards \| Non-officer employees
Stock-based Compensation
Vesting period						3 years	3 years	3 years
Target performance awards \| Officers
Stock-based Compensation
Vesting period						3 years	3 years
Target performance awards \| Minimum
Stock-based Compensation
Percentage of target award, which can be earned by each eligible employee							25.00%
Target performance awards \| Maximum
Stock-based Compensation
Percentage of target award, which can be earned by each eligible employee							125.00%
Target performance awards \| Discontinued Operations, Disposed of by Means Other than Sale, Spinoff \| SPX Flow, Inc
Stock-based Compensation
Percentage of target award, which can be earned by each eligible employee							50.00%
Additional stock compensation expense \| $						$ 2.1
Stock options
Stock-based Compensation
Vesting period						3 years
Options outstanding (in shares) \| shares						505,000.000	0
Assumptions in determining the fair value of awards granted
Annual expected stock price volatility (as a percent)	27.86%	36.53%
Annual expected dividend yield (as a percent)	0.00%	1.75%
Risk-free interest rate (as a percent)	1.64%	1.97%
Expected Life of Options (in years)	6 years	6 years
Historical period upon which annual expected stock price volatility is based						6 years
Daily treasury yield curve period upon which average risk-free interest rate is based						7 years