Debt (Schedule Of Notes Payable And Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Short-term Debt, Weighted Average Interest Rate	0.20%	0.20%
Long-term Debt, Weighted Average Interest Rate, Current Maturities	0.00%	0.00%
Debt, Current	$ 89	$ 383
Debt, Weighted Average Interest Rate, Short-term and Current Maturities of Long-term Debt	0.20%	0.20%
Long-term Debt, Weighted Average Interest Rate, Noncurrent Maturities	3.40%	3.40%
Long-term Debt, Weighted Average Interest Rate	3.40%	3.40%
Commercial Paper [Member]
Debt Instrument [Line Items]
Short-term Debt	89	381
Short-term Debt, Weighted Average Interest Rate	0.20%	0.20%
$200.0 European Revolving Credit Facility, Due March 13, 2014 [Member]
Debt Instrument [Line Items]
Short-term Debt	0	0
Short-term Debt, Weighted Average Interest Rate	0.00%	0.00%
Sigma-Aldrich Korea Limited Credit Facility, Due June 30, 2013 [Member]
Debt Instrument [Line Items]
Short-term Debt	0	0
Short-term Debt, Weighted Average Interest Rate	0.00%	0.00%
Sigma-Aldrich Japan Credit Facility [Member]
Debt Instrument [Line Items]
Short-term Debt	0	0
Short-term Debt, Weighted Average Interest Rate	0.00%	0.00%
Other Short-Term Credit Facilities [Member]
Debt Instrument [Line Items]
Short-term Debt	0	2
Short-term Debt, Weighted Average Interest Rate	0.00%	1.50%
Senior Notes, Due November 1, 2020 [Member]
Debt Instrument [Line Items]
Outstanding	300
Long-term Debt, Weighted Average Interest Rate, Noncurrent Maturities	3.40%	3.40%
Total Notes Payable [Member]
Debt Instrument [Line Items]
Short-term Debt	89	383
Plus-Current Maturities Of Long-Term Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	0	0
Total Notes Payable And Current Maturities Of Long-Term Debt [Member]
Debt Instrument [Line Items]
Debt, Current	89	383
Long-Term Debt [Member]
Debt Instrument [Line Items]
Outstanding	300	300
Long-Term Debt [Member] | Senior Notes, Due November 1, 2020 [Member]
Debt Instrument [Line Items]
Outstanding	300	300
Less - Current Maturities [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	0	0
Total Long-Term Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 300	$ 300