Fair Value Measurements (Narrative) (Details) (6.25% Senior Notes [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Face amount	$ 550
Interest rate	6.25%
Level 2 Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 638	$ 674