Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales		$ 282.4	$ 263.4	$ 794.9	$ 785.1
Cost of goods sold		175.9	154.8	488.1	465.1
Gross profit		106.5	108.6	306.8	320.0
Selling, general and administrative expenses		76.3	67.4	221.9	199.5
Research and development expenses		5.2	4.7	15.2	13.6
Interest expense and related financing costs		21.6	18.8	56.1	49.0
Repositioning expenses		1.1	5.3	6.8	14.3
Restructuring expenses and asset impairments		2.1	0.4	13.0	1.4
Loss in Venezuela		36.7	0.0	38.3	0.0
Other income, net		(4.0)	(1.6)	(6.6)	(1.7)
Total costs and expenses		139.0	95.0	344.7	276.1
(Loss) income from continuing operations before income taxes		(32.5)	13.6	(37.9)	43.9
Income tax benefit (expense)		14.5	(2.5)	(3.7)	(9.8)
(Loss) income from continuing operations		(18.0)	11.1	(41.6)	34.1
Income from discontinued operations, net of income taxes		677.3	10.4	679.4	36.2
Net income		659.3	21.5	637.8	70.3
Less: Net income attributable to noncontrolling interests		(0.1)	(0.2)	(0.2)	(0.9)
Net income attributable to GCP shareholders		659.2	21.3	637.6	69.4
Amounts Attributable to GCP Shareholders:
(Loss) income from continuing operations attributable to GCP shareholders		(18.1)	10.9	(41.8)	33.2
Income from discontinued operations, net of income taxes		677.3	10.4	679.4	36.2
Net income attributable to GCP shareholders		$ 659.2	$ 21.3	$ 637.6	$ 69.4
Basic earnings per share:
Net (loss) income from continuing operations attributable to GCP shareholders (in usd per share)		$ (0.25)	$ 0.15	$ (0.59)	$ 0.47
Income from discontinued operations, net of income taxes (in usd per share)		9.46	0.15	9.54	0.51
Net income attributable to GCP shareholders (in usd per share)	[1]	$ 9.21	$ 0.30	$ 8.96	$ 0.98
Weighted average number of basic shares		71.6	71.0	71.2	70.8
Diluted earnings per share:
Net (loss) income from continuing operations attributable to GCP shareholders (in usd per share)	[2]	$ (0.25)	$ 0.15	$ (0.59)	$ 0.46
Income from discontinued operations, net of income taxes (in usd per share)	[2]	9.46	0.14	9.54	0.51
Net income attributable to GCP shareholders (in usd per share)	[1],[2]	$ 9.21	$ 0.30	$ 8.96	$ 0.97
Weighted average number of diluted shares		71.6	72.2	71.2	71.6

[1] Amounts may not sum due to rounding

[2] Dilutive effect only applicable to periods where there is net income from continuing operations.