Consolidated Statements of Equity (Deficit) (unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Net Parent Investment	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Beginning balance at Dec. 31, 2015	$ 474.1	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 598.3	$ (127.7)	$ 3.5
Beginning balance, shares at Dec. 31, 2015		0.0	0.0
Increase (Decrease) in Stockholders' Equity
Net income	18.2				10.6	7.2		0.4
Net transfer to parent	(677.9)					(677.9)
Issuance of common stock and reclassification of net parent investment in connection with Separation, shares		70.5
Issuance of common stock and reclassification of net parent investment in connection with Separation	0.0	$ 0.7			(73.1)	72.4
Issuance of common stock in connection with stock plans, shares		0.1
Share-based compensation	0.7			0.7
Exercise of stock options, shares		0.2
Exercise of stock options	0.6			0.6
Treasury stock purchased under GCP 2016 Stock Incentive Plan, shares			0.1
Treasury stock purchased under GCP 2016 Stock Incentive Plan	(1.7)		$ (1.7)
Other comprehensive income	3.9						3.7	0.2
Ending balance at Mar. 31, 2016	(182.1)	$ 0.7	$ (1.7)	1.3	(62.5)	$ 0.0	(124.0)	4.1
Ending balance, shares at Mar. 31, 2016		70.8	0.1
Beginning balance at Dec. 31, 2016	(139.0)	$ 0.7	$ (2.1)	11.0	(4.7)		(147.6)	3.7
Beginning balance, shares at Dec. 31, 2016		71.2	0.1
Increase (Decrease) in Stockholders' Equity
Net income	(16.9)				(16.9)
Issuance of common stock in connection with stock plans, shares		0.1
Share-based compensation	2.1			2.1
Exercise of stock options, shares		0.3
Exercise of stock options	4.1			4.1
Treasury stock purchased under GCP 2016 Stock Incentive Plan	(0.9)		$ (0.9)
Other comprehensive income	12.6						12.6
Dividends and other changes in noncontrolling interest	0.3							0.3
Ending balance at Mar. 31, 2017	$ (137.7)	$ 0.7	$ (3.0)	$ 17.2	$ (21.6)		$ (135.0)	$ 4.0
Ending balance, shares at Mar. 31, 2017		71.6	0.1