Financing Arrangements (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Arrangements (Textual) [Abstract]
Borrowings outstanding	$ 0	$ 0
Weighted average interest rate on short-term debt	3.20%	4.10%	4.30%
Weighted average interest rate on short-term debt, outstanding	1.50%	3.60%
Total Long-term debt	464.7	493.1
Restricted cash as Collateral account for Credit Facility of AGC from US Bank	0	3.6
Amount Reserved in Collateral Account		3.6
Maturities of long-term debt in 2013	9.6
Maturities of long-term debt in 2014	249.9
Maturities of long-term debt in 2015	0
Maturities of long-term debt in 2016	15.0
Maturities of long-term debt in 2017	5.0
Debt instrument yield rate	1.06%	1.25%	1.34%
Interest paid	32	35	36
Interest capitalized	4.9	1.2	0.7
Rent expense under operating leases	43.6	44.5	38.1
Future minimum lease payments for noncancelable operating leases total	122.2
Future minimum lease payments for noncancelable operating leases 2013	35.4
Future minimum lease payments for noncancelable operating leases 2014	29.2
Future minimum lease payments for noncancelable operating leases 2015	21.7
Future minimum lease payments for noncancelable operating leases 2016	14.9
Future minimum lease payments for noncancelable operating leases 2017	9.6
Future minimum lease payments for noncancelable operating leases thereafter	11.4
Ohio Pollution Control Revenue Refunding Bonds [Member]
Financing Arrangements (Textual) [Abstract]
Total Long-term debt	8.5	17.0
Debt Instruments, Maturity Date	Jun. 01, 2033
Corporate Joint Venture [Member]
Financing Arrangements (Textual) [Abstract]
Credit Facility with AGC from US Bank		3.6
Foreign Subsidiary [Member]
Financing Arrangements (Textual) [Abstract]
Maximum borrowing capacity under line of credit	225.6
Borrowings outstanding	14.3
Remaining Borrowing Capacity under Line of Credit Facility of Company's foreign subsidiaries	211.3
Line of Credit Accounts Receivable Securitization [Member]
Financing Arrangements (Textual) [Abstract]
Maximum borrowing capacity under line of credit	200.0	150.0
Line of Credit Facility, Current Borrowing Capacity	154.2
Line of credit expiration date	Nov. 30, 2015
Senior Credit Facility [Member]
Financing Arrangements (Textual) [Abstract]
Maximum borrowing capacity under line of credit	500.0
Borrowings outstanding	0
Remaining Borrowing Capacity under Line of Credit Facility of Company's foreign subsidiaries	491.4
Line of credit expiration date	May 11, 2016
Number of Financial Covenant under senior Credit Facility	2
Senior Credit Facility Letters of Credit [Member]
Financing Arrangements (Textual) [Abstract]
Borrowings outstanding	8.6
Foreign Subsidiary Long Term Borrowings [Member]
Financing Arrangements (Textual) [Abstract]
Maximum borrowing capacity under line of credit	9.6
Borrowings outstanding	9.6
Remaining Borrowing Capacity under Line of Credit Facility of Company's foreign subsidiaries	$ 0