Reconciliation of Reportable Segment Operating Income and Segment Assets to Corresponding Consolidated Amounts (Parenthetical) (Detail) (Securities Litigation, USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Sep. 30, 2012
Securities Litigation
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net insurance proceeds	$ 3.3	$ 3.3