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Employee Retirement Plans (Details) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended9 Months Ended3 Months Ended9 Months Ended3 Months Ended9 Months Ended
Jun. 30, 2011
Sep. 30, 2011
Pension [Member]
Sep. 30, 2010
Pension [Member]
Sep. 30, 2011
Pension [Member]
Sep. 30, 2010
Pension [Member]
Sep. 30, 2011
Postretirement [Member]
Sep. 30, 2010
Postretirement [Member]
Sep. 30, 2011
Postretirement [Member]
Sep. 30, 2010
Postretirement [Member]
Sep. 30, 2011
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member]
Sep. 30, 2011
Foreign Postretirement Benefit Plans, Defined Benefit [Member]
Components of net pension and postretirement benefits costs           
Service cost of benefits earned $ 7$ 7$ 21$ 20$ 1$ 1$ 4$ 5  
Interest cost on projected benefit obligation 15164748341013  
Expected return on plan assets (16)(16)(49)(49)      
Net amortization 732011(5)(4)(16)(13)  
Net cost 13103930(1)1(2)5  
Employee Retirement Plans (Textual) [Abstract]           
Contribution by employer   30.9     10.010.0
Contribution by employer in common stock   2,084,781       
Aggregate Contribution by employer   $ 30.0       
Closing price per share of contributed shares to the USG corporation Retirement plan Trust$ 14.84          
Discounted value shares valued for purposes of crediting the contribution to trust$ 14.39          
Discount rate used to valued shares for purposes of crediting the contribution to the Trust3.00%          
Rate at which shares valued for purposes of crediting the contribution to trust$ 14.84