Debt (Schedule Of Notes Payable And Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Total Notes Payable [Member]
Debt Instrument [Line Items]
Outstanding	$ 373		$ 221
Debt, Weighted Average Interest Rate	0.20%		0.10%
Total Notes Payable [Member] | Commercial Paper [Member]
Debt Instrument [Line Items]
Outstanding	373	[1]	221	[1]
Debt, Weighted Average Interest Rate	0.20%	[1]	0.10%	[1]
Total Notes Payable [Member] | $200.0 European Revolving Credit Facility, Due March 13, 2014 [Member]
Debt Instrument [Line Items]
Outstanding	0	[2]	0	[2]
Debt, Weighted Average Interest Rate	0.00%	[2]	0.00%	[2]
Total Notes Payable [Member] | Sigma-Aldrich Korea Limited Credit Facility, Due June 30, 2013 [Member]
Debt Instrument [Line Items]
Outstanding	0	[3]	0	[3]
Debt, Weighted Average Interest Rate	0.00%	[3]	0.00%	[3]
Total Notes Payable [Member] | Sigma-Aldrich Japan Credit Facility [Member]
Debt Instrument [Line Items]
Outstanding	0	[4]	0	[4]
Debt, Weighted Average Interest Rate	0.00%	[4]	0.00%	[4]
Total Notes Payable [Member] | Other Short-Term Credit Facilities [Member]
Debt Instrument [Line Items]
Outstanding	0	[5]	0	[5]
Debt, Weighted Average Interest Rate	0.00%	[5]	0.00%	[5]
Plus-Current Maturities Of Long-Term Debt [Member]
Debt Instrument [Line Items]
Outstanding	0		0
Debt, Weighted Average Interest Rate	0.00%		0.00%
Total Notes Payable And Current Maturities Of Long-Term Debt [Member]
Debt Instrument [Line Items]
Outstanding	373		221
Debt, Weighted Average Interest Rate	0.20%		0.10%
Long-Term Debt [Member]
Debt Instrument [Line Items]
Outstanding	300		300
Debt, Weighted Average Interest Rate	3.40%		3.40%
Long-Term Debt [Member] | Senior Notes, Due November 1, 2020 [Member]
Debt Instrument [Line Items]
Outstanding	300	[6]	300	[6]
Debt, Weighted Average Interest Rate	3.40%	[6]	3.40%	[6]
Less - Current Maturities [Member]
Debt Instrument [Line Items]
Outstanding	0		0
Debt, Weighted Average Interest Rate	0.00%		0.00%
Total Long-Term Debt [Member]
Debt Instrument [Line Items]
Outstanding	$ 300		$ 300
Debt, Weighted Average Interest Rate	3.40%		3.40%

[1] On May 10, 2012, the Company entered into a new $600 five-year revolving credit facility with a syndicate of banks in the U.S. that supports the Company’s commercial paper program. The new facility will mature on May 9, 2017, and replaces a $450 revolving credit facility that was scheduled to mature on December 11, 2012. At September 30, 2012 and December 31, 2011, the Company did not have any borrowings outstanding under these facilities. The new facility contains a financial covenant that requires the maintenance of a ratio of consolidated debt to total capitalization of no more than 65.0 percent. The Company’s total consolidated debt as a percentage of total capitalization, as defined in the underlying credit agreement, was 22.5 percent at September 30, 2012.

[2] Facility contains financial covenants that require the maintenance of consolidated net worth of at least $750 and a ratio of consolidated debt to total capitalization of no more than 55.0 percent. The Company’s consolidated net worth and consolidated debt as a percentage of total capitalization, as defined in the underlying credit agreement, were $2,313 and 22.5 percent, respectively, at September 30, 2012.

[3] There were no outstanding borrowings under this facility, which has a total commitment of 20 billion Korean Won ($18), at September 30, 2012.

[4] Sigma-Aldrich Japan has two credit facilities having a total commitment of 2 billion Japanese Yen ($26), with one facility due April 30, 2013 and the other representing a line of credit with no expiration. There were no borrowings under the facilities at September 30, 2012.

[5] There were no borrowings under these facilities, which have total commitments in U.S. Dollar equivalents of $3, at September 30, 2012.

[6] The Company has $300 of 3.375 percent Senior Notes due November 1, 2020. Interest on the notes is payable May 1 and November 1 of each year. The notes may be redeemed, in whole or in part at the Company’s option, (i) at any time at specific redemption prices plus accrued interest or (ii) three months prior to the maturity date at a redemption price equal to 100 percent of the principal amount plus accrued interest.