Charges and Credits - Repurchase of Debt (Parenthetical) (Detail)	Dec. 31, 2010	Sep. 30, 2010
6.50% Notes due 2012 [Member]
Restructuring Cost and Reserve [Line Items]
Interest rate	6.50%	6.50%
6.75% Senior Notes due 2011 [Member]
Restructuring Cost and Reserve [Line Items]
Interest rate	6.75%
9.75% Senior Notes due 2019 [Member]
Restructuring Cost and Reserve [Line Items]
Interest rate	9.75%
6.00% Senior Notes due 2016 [Member]
Restructuring Cost and Reserve [Line Items]
Interest rate	6.00%
8.625% Senior Notes due 2014 [Member]
Restructuring Cost and Reserve [Line Items]
Interest rate	8.625%