Postretirement Benefit Plans - Changes in Fair Value of Plan Assets of Pension and Other Employee-Related Defined Benefit Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015
Change in plan assets
Plan assets - January 1	$ 286.9		$ 283.4
Actual return on plan assets	24.5		(7.9)
Employer contributions	19.0		18.6
Benefits and expenses paid	(32.7)		(29.1)
Acquired	0.0		23.1
Settlement(a)	(28.5)		(1.1)
Foreign currency translation	0.0		(0.1)
Plan assets - December 31	269.2		286.9
Funded status at end of year	(261.8)		(274.4)
U.S. Pension Plans [Member]
Change in plan assets
Plan assets - January 1	278.1		272.9
Actual return on plan assets	24.0		(8.0)
Employer contributions	9.6		8.6
Benefits and expenses paid	(21.5)		(18.5)
Acquired	0.0		23.1
Settlement(a)	(28.0)	[1]	0.0
Foreign currency translation	0.0		0.0
Plan assets - December 31	262.2		278.1
Funded status at end of year	(50.1)		(61.8)
International Pension Plan [Member]
Change in plan assets
Plan assets - January 1	0.9		1.0
Actual return on plan assets	0.0		0.0
Employer contributions	3.2		3.8
Benefits and expenses paid	(2.7)		(2.7)
Acquired	0.0		0.0
Settlement(a)	(0.5)		(1.1)
Foreign currency translation	0.0		(0.1)
Plan assets - December 31	0.9		0.9
Funded status at end of year	(79.0)		(77.1)
Other Postretirement Benefit Plan [Member]
Change in plan assets
Plan assets - January 1	7.9		9.5
Actual return on plan assets	0.5		0.1
Employer contributions	6.2		6.2
Benefits and expenses paid	(8.5)		(7.9)
Acquired	0.0		0.0
Settlement(a)	0.0		0.0
Foreign currency translation	0.0		0.0
Plan assets - December 31	6.1		7.9
Funded status at end of year	$ (132.7)		$ (135.5)

[1] (a)During 2016, we recognized a non-cash pretax pension settlement charge of $12.7 as the result of a program offering certain former U.S. employees with a vested pension benefit an option to take a one-time lump sum distribution as part of ITT's overall plan to de-risk its pension plans. Approximately 1,100 participants accepted the offer, resulting in a payment of $28.0 from the plan and a reduction in the Company's projected benefit obligation of $26.6, including an actuarial loss of $1.4.