Chapter 11 Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended		132 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2012 Chapter 11 Filing Entities	Mar. 31, 2011 Chapter 11 Filing Entities	Mar. 31, 2012 Chapter 11 Filing Entities	Dec. 31, 2011 Chapter 11 Filing Entities	Apr. 02, 2001 Chapter 11 Filing Entities
Components of liabilities subject to compromise are as follows:
Asbestos-related contingencies	$ 1,700.0		$ 1,700.0		$ 1,700.0		$ 1,700.0	$ 1,700.0
Pre-petition bank debt plus accrued interest	949.5		941.8		914.6		914.6	907.3
Environmental contingencies	146.3		149.9		146.3		146.3	149.9
Unfunded special pension arrangements	184.3		185.2		129.5		129.5	129.0
Income tax contingencies	70.3		69.3		70.3		70.3	69.3
Postretirement benefits other than pension					64.1		64.1	64.6
Drawn letters of credit plus accrued interest					34.9		34.9	34.5
Accounts payable					31.3		31.3	31.3
Retained obligations of divested businesses					29.0		29.0	28.4
Other accrued liabilities	152.3		149.5		92.0		92.0	89.8
Reclassification to current liabilities					(9.3)		(9.3)	(8.4)
Total Liabilities Subject to Compromise	3,202.7		3,195.7		3,202.7		3,202.7	3,195.7	2,366.0
Reconciliation of the changes in pre-filing date liability balances
Balance, Filing Date April 2, 2001									2,366.0
Cash disbursements and/or reclassifications under Bankruptcy Court orders:
Payment of environmental settlement liability	4.4	2.4					(252.0)
Freight and distribution order							(5.7)
Trade accounts payable order							(9.1)
Resolution of contingencies subject to Chapter 11							(130.0)
Other court orders for payments of certain operating expenses							(364.9)
Expense/(income) items:
Interest on pre-petition liabilities							519.5
Employee-related accruals							115.2
Provision for asbestos-related contingencies							744.8
Provision for environmental contingencies							352.7
Provision for income tax contingencies							(98.8)
Balance sheet reclassifications							(35.0)
Balance, end of period							3,202.7
Chapter 11 Expenses
Legal and financial advisory fees					4.7	6.0
Interest (income) expense					(0.2)	(0.2)
Chapter 11 expenses, net of interest income	4.5	5.8			4.5	5.8
Debtor-in-Possession Statements of Operations
Net sales, including intercompany	754.4	695.7			364.3	314.3
Cost of goods sold, including intercompany, exclusive of depreciation and amortization shown separately below					226.0	183.2
Selling, general and administrative expenses	136.6	129.9			67.5	65.2
Defined benefit pension expense	18.8	16.5			13.5	11.6
Depreciation and amortization	29.4	29.2			16.5	16.9
Chapter 11 expenses, net of interest income	4.5	5.8			4.5	5.8
Research and development expenses	16.5	15.6			9.3	9.0
Interest expense and related financing costs	11.3	10.4			10.3	9.8
Restructuring expenses					2.4	0.2
Provision for environmental remediation	0.6	0.2			0.4
Other income, net	(0.6)	(2.2)			(12.6)	(14.0)
Total costs and expenses	185.0	172.9			337.8	287.7
Income before income taxes and equity in net income of non-filing entities					26.5	26.6
Provision for income taxes	(30.8)	(25.5)			(10.0)	(10.7)
Income before equity in net income of non-filing entities					16.5	15.9
Equity in net income of non-filing entities					44.4	38.3
Net income attributable to W. R. Grace & Co. shareholders	60.9	54.2			60.9	54.2
OPERATING ACTIVITIES
Net income attributable to W. R. Grace & Co. shareholders	60.9	54.2			60.9	54.2
Reconciliation to net cash used for operating activities:
Depreciation and amortization	29.4	29.2			16.5	16.9
Equity in net income of non-filing entities					(44.4)	(38.3)
Provision for income taxes	30.8	25.5			10.0	10.7
Income taxes paid, net of refunds	(8.0)	(23.9)			(0.2)	(15.4)
Defined benefit pension expense	18.8	16.5			13.5	11.6
Payments under defined benefit pension arrangements	(113.7)	(207.3)			(110.7)	(204.5)
Changes in assets and liabilities, excluding the effect of foreign currency translation:
Trade accounts receivable	11.1	(37.8)			6.3	(21.6)
Inventories	(26.1)	(38.5)			11.5	(16.5)
Accounts payable	(1.2)	45.4			(23.9)	24.2
All other items, net	(41.8)	(47.6)			(23.0)	(13.3)
Net cash used for operating activities					(83.5)	(192.0)
INVESTING ACTIVITIES
Capital expenditures	(25.0)	(23.4)			(15.7)	(13.3)
Transfer to restricted cash and cash equivalents	(3.0)	(0.6)			(6.9)
Other		(0.1)				0.2
Net cash used for investing activities					(22.6)	(13.1)
Net cash provided by (used for) financing activities					12.9	(1.3)
Net decrease in cash and cash equivalents					(93.2)	(206.4)
Cash and cash equivalents, beginning of period	1,048.3	1,015.7			788.6	787.2
Cash and cash equivalents, end of period	1,008.2	819.4			695.4	580.8	695.4
Current Assets
Cash and cash equivalents	1,008.2	819.4			695.4	580.8	695.4
Restricted cash and cash equivalents	139.6		136.5		89.8		89.8	82.9
Trade accounts receivable, net	458.0		461.8		119.2		119.2	125.5
Accounts receivable-unconsolidated affiliate	13.7		11.2		13.2		13.2	10.2
Receivables from non-filing entities, net					150.4		150.4	143.1
Inventories	358.5		329.1		148.5		148.5	160.0
Other current assets	86.5		93.0		62.5		62.5	67.3
Total Current Assets	2,133.2		2,146.4		1,279.0		1,279.0	1,377.6
Properties and equipment, net	726.8		723.5		418.0		418.0	418.8
Deferred income taxes	735.0		759.4		721.9		721.9	752.7
Asbestos-related insurance	500.0		500.0		500.0		500.0	500.0
Loans receivable from non-filing entities, net					371.9		371.9	362.3
Investment in non-filing entities					369.4		369.4	333.6
Investment in unconsolidated affiliate	76.4		70.8		76.4		76.4	70.8
Other Assets	104.9		108.6		60.6		60.6	63.7
Total Assets	4,460.0		4,494.0		3,797.2		3,797.2	3,879.5
Liabilities Not Subject to Compromise
Current liabilities (including $7.5 due to unconsolidated affiliate) (2011-$3.5)	617.3		632.9		212.6		212.6	250.7
Underfunded defined benefit pension plans					75.9		75.9	215.5
Other liabilities (including $19.4 due to unconsolidated affiliate) (2011-$18.3)	45.6		49.1		55.1		55.1	58.1
Total Liabilities Not Subject to Compromise	997.9		1,130.8		343.6		343.6	524.3
Liabilities Subject to Compromise	3,202.7		3,195.7		3,202.7		3,202.7	3,195.7	2,366.0
Total Liabilities	4,200.6		4,326.5		3,546.3		3,546.3	3,720.0
Total W. R. Grace & Co. Shareholders' Equity (Deficit)	250.8		159.4		250.8		250.8	159.4
Noncontrolling interests in Chapter 11 filing entities	8.6		8.1		0.1		0.1	0.1
Total Equity (Deficit)	259.4	4.2	167.5	(68.8)	250.9		250.9	159.5
Total Liabilities and Equity (Deficit)	4,460.0		4,494.0		3,797.2		3,797.2	3,879.5
Due to unconsolidated affiliate, current					7.5		7.5	3.5
Due to unconsolidated affiliate, noncurrent					$ 19.4		$ 19.4	$ 18.3