Debt (Schedule of Long-term Debt) (Details) (USD $) In Millions, unless otherwise specified			3 Months Ended	12 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended	1 Months Ended			9 Months Ended			3 Months Ended		3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Term C Loan Facility [Member]	Dec. 31, 2012 Term C Loan Facility [Member]	Sep. 30, 2010 Senior Unsecured Notes Due 2018 [Member]	Mar. 31, 2013 Senior Unsecured Notes Due 2018 [Member]	Dec. 31, 2012 Senior Unsecured Notes Due 2018 [Member]	May 31, 2011 Senior Unsecured Notes Due 2021 [Member]	Mar. 31, 2013 Senior Unsecured Notes Due 2021 [Member]	Dec. 31, 2012 Senior Unsecured Notes Due 2021 [Member]	Nov. 30, 2012 Senior Unsecured Notes Due 2022 [Member]	Mar. 31, 2013 Senior Unsecured Notes Due 2022 [Member]	Dec. 31, 2012 Senior Unsecured Notes Due 2022 [Member]	Sep. 30, 2010 Credit-Linked Revolving Facility [Member]	Mar. 31, 2013 Credit-Linked Revolving Facility [Member]	Dec. 31, 2012 Credit-Linked Revolving Facility [Member]	Mar. 31, 2013 Pollution Control and Industrial Revenue Bonds [Member]	Dec. 31, 2012 Pollution Control and Industrial Revenue Bonds [Member]	Mar. 31, 2013 Obligations Under Capital Leases [Member]	Dec. 31, 2012 Obligations Under Capital Leases [Member]	Mar. 31, 2013 Other Bank Obligations [Member]	Dec. 31, 2012 Other Bank Obligations [Member]
Long-Term Debt
Senior credit facilities			$ 967	$ 977											$ 100	$ 50
Senior unsecured notes						600	600		400	400		500	500
Year of maturity			Oct. 31, 2016	Oct. 31, 2016	Oct. 15, 2018	Oct. 15, 2018	Oct. 15, 2018	Jun. 15, 2021	Jun. 15, 2021	Jun. 15, 2021	Nov. 15, 2022
Interest rate, stated percentage					6.625%	6.625%	6.625%	5.875%	5.875%	5.875%	4.625%
Credit facility, expiration date														Apr. 02, 2014
Credit facility, interest rate															1.70%
Other long-term debt																	169	182
Interest rate, stated percentage range, minimum																	5.70%
Interest rate, stated percentage range, maximum																	6.70%
Year of maturity, range end																	Nov. 01, 2030		Mar. 31, 2054
Capital lease obligations																			246	244
Other loans payable																					0	37
Subtotal	2,982	2,990
Current installments of long-term debt	(23)	(60)
Total	$ 2,959	$ 2,930