Postretirement Benefit Plans - Additional Information (Detail) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Participant Rate shares	Dec. 31, 2016 USD ($) Employees	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Company contributions to defined contribution plans	$ 16.7	$ 17.3	$ 18.4
Shares of ITT Stock Held in Defined Contribution Plan | shares	0.2
Active participants in numerous defined benefit pension plans | Participant	2,000
Accumulated benefit obligation	$ 416.7	$ 389.4
Number of Employees Offered a Pension Settlement | Employees		1,100
Defined Benefit Plan, Plan Assets, Payment for Settlement	0.4	$ 28.5
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 0.4	$ 28.5
Assumed rate of future decrease in per capita cost of health care for 2027	4.50%
Effect of one percent increase on benefit obligation	$ 7.5
Effect of one percent increase on annual service and interest cost components	0.3
Effect of one percent decrease on benefit obligation	6.4
Effect of one percent decrease on annual service and interest cost components	$ 0.3
Reduction to Investment Target Allocation for Fixed Income	20.00%		15.00%
Long-term annual rate of return for domestic pension plans	7.00%	7.20%	8.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Return on Assets, Estimate for Next Year	6.00%
Contributions to postretirement plans	$ 45.0	$ 19.0	$ 18.6
Employer contributions	45.0	19.0
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Curtailment or settlement charges	3.7	12.7	0.1
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		1.4
Contributions to postretirement plans	38.9	12.8
Discretionary Pension Contribution	35.0	7.8
Defined Benefit Plan, Expected Employer Contributions Next Fiscal Year	5.0
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Curtailment or settlement charges	0.0	0.0	(4.2)
Defined Benefit Plan, Plan Assets, Payment for Settlement	0.0	0.0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 0.0	$ 0.0
Long-term annual rate of return for domestic pension plans	7.00%	7.20%
Defined Benefit Plan, Expected Employer Contributions Next Fiscal Year	$ 8.0
Employer contributions	$ 6.1	$ 6.2
International Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	22.00%
International Plan [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Curtailment or settlement charges	$ 0.0	0.0	0.1
Defined Benefit Plan, Plan Assets, Payment for Settlement	0.4	0.5
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 0.4	$ 0.5
Long-term annual rate of return for domestic pension plans	1.00%	4.80%
Employer contributions	$ 3.0	$ 3.2
U.S. Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		26.6
U.S. Plan [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Curtailment or settlement charges	3.7	12.7	$ 0.0
Defined Benefit Plan, Plan Assets, Payment for Settlement	0.0	28.0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 0.0	$ 28.0
Long-term annual rate of return for domestic pension plans	7.00%	7.20%
Employer contributions	$ 35.9	$ 9.6
Pre Age Sixty Five [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumed rate of future increase in per capita cost of health care for 2018	7.00%
Post-age 65 retirees [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumed rate of future increase in per capita cost of health care for 2018	6.50%
Pension Plan For Bargaining Unit Employees Seneca Falls [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	35.00%
Consolidated Hourly Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	39.00%
Other Non Qualified Us Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation	4.00%
Equity Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | Rate	30.00%
Fixed Income Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | Rate	70.00%