Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net sales		$ 216.7	$ 226.1
Cost of goods sold		134.8	143.9
Gross profit		81.9	82.2
Selling, general and administrative expenses		68.1	69.0
Research and development expenses		4.9	4.7
Interest expense and related financing costs		5.7	5.9
Repositioning expenses		2.7	5.4
Restructuring expenses and asset impairments		3.1	0.6
Other income, net		(2.2)	(1.8)
Total costs and expenses		82.3	83.8
Loss from continuing operations before income taxes		(0.4)	(1.6)
Benefit from income taxes		1.9	16.4
Income from continuing operations		1.5	14.8
(Loss) income from discontinued operations, net of income taxes		(0.3)	6.8
Net income		1.2	21.6
Less: Net income attributable to noncontrolling interests		(0.1)	(0.2)
Net income attributable to GCP shareholders		1.1	21.4
Amounts Attributable to GCP Shareholders:
Income from continuing operations attributable to GCP shareholders		1.4	14.6
(Loss) income from discontinued operations, net of income taxes		(0.3)	6.8
Net income attributable to GCP shareholders		$ 1.1	$ 21.4
Basic earnings (loss) per share:
Income from continuing operations attributable to GCP shareholders (in usd per share)		$ 0.02	$ 0.20
(Loss) income from discontinued operations, net of income taxes (in usd per share)		0	0.09
Net income attributable to GCP shareholders (in usd per share)	[1]	$ 0.02	$ 0.30
Weighted average number of basic shares (in shares)		72.9	72.3
Diluted earnings (loss) per share:
Income from continuing operations attributable to GCP shareholders (in dollars per share)	[2]	$ 0.02	$ 0.20
(Loss) income from discontinued operations, net of income taxes (in dollars per share)	[2]	0	0.09
Net income attributable to GCP shareholders (in dollars per share)	[1],[2]	$ 0.02	$ 0.29
Weighted average number of diluted shares (in shares)	[2]	73.0	72.8

[1] Amounts may not sum due to rounding.

[2] Dilutive effect is only applicable to the periods during which GCP generated net income from continuing operations.