Goodwill and Other Intangible Assets (Narrative) (Detail) (USD $)	1 Months Ended	3 Months Ended			3 Months Ended				6 Months Ended
	May 31, 2012	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 Selling, General And Administrative Expenses [Member]	Mar. 31, 2012 Selling, General And Administrative Expenses [Member]	Mar. 31, 2013 Selling, General And Administrative Expenses [Member]	Dec. 31, 2012 Selling, General And Administrative Expenses [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill		$ 493,000,000	$ 480,000,000	$ 480,000,000
Goodwill annual impairment	0
Useful life of intangible assets		19 years			6 years	20 years
Amortization of Intangible assets							3,000,000	1,000,000	6,000,000	1,000,000
Amortization expense estimated for year one		14,000,000
Amortization expense estimated for year two		14,000,000
Amortization expense estimated for year three		14,000,000
Amortization expense estimated for year four		14,000,000
Amortization expense estimated for year five		$ 14,000,000