Postretirement Benefit Plans - Changes in Projected Benefit Obligations of Pension and Other Employee-Related Defined Benefit Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Change in benefit obligation
Benefit obligation – January 1	$ 546.1	$ 532.6
Service cost	5.9	6.3
Interest cost	19.5	22.9
Amendments(a)	0.0	(54.2)
Actuarial (gain) loss	(10.8)	78.6
Benefits and expenses paid	(29.1)	(28.1)
Acquired	37.4	0.0
Settlement	(1.1)	(1.6)
Curtailment	2.0	0.0
Foreign currency translation	(8.6)	(10.4)
Benefit obligation – December 31	561.3	546.1		$ 532.6
U.S. Pension Plans [Member]
Change in benefit obligation
Benefit obligation – January 1	324.1	281.2
Service cost	3.5	3.2		4.9
Interest cost	13.0	13.1		12.1
Amendments(a)	0.0	4.5
Actuarial (gain) loss	(14.9)	39.0
Benefits and expenses paid	(18.5)	(16.9)
Acquired	32.7	0.0
Settlement	0.0	0.0
Curtailment	0.0	0.0
Foreign currency translation	0.0	0.0
Benefit obligation – December 31	339.9	324.1		281.2
International Pension Plan [Member]
Change in benefit obligation
Benefit obligation – January 1	87.5	84.8
Service cost	1.5	1.6		1.7
Interest cost	1.5	2.4		2.5
Amendments(a)	0.0	0.0
Actuarial (gain) loss	(2.9)	13.7
Benefits and expenses paid	(2.7)	(3.0)
Acquired	2.8	0.0
Settlement	(1.1)	(1.6)
Curtailment	0.0	0.0
Foreign currency translation	(8.6)	(10.4)
Benefit obligation – December 31	78.0	87.5		84.8
Other Postretirement Benefit Plan, Defined Benefit [Member]
Change in benefit obligation
Benefit obligation – January 1	134.5	166.6
Service cost	0.9	1.5		2.9
Interest cost	5.0	7.4		8.3
Amendments(a)	0.0	(58.7)	[1]
Actuarial (gain) loss	7.0	25.9
Benefits and expenses paid	(7.9)	(8.2)
Acquired	1.9	0.0
Settlement	0.0	0.0
Curtailment	2.0	0.0
Foreign currency translation	0.0	0.0
Benefit obligation – December 31	$ 143.4	$ 134.5		$ 166.6

[1] (a)During 2014, management approved changes to certain other employee-related defined benefit plans, reducing certain retiree medical benefits, resulting in a decrease to ITT's other employee-related defined benefit liability of $58.7.