Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		12 Months Ended
	Oct. 31, 2010 Securities Class Action (Apollo Institutional Investors Group) [Member] Plaintiffs	Jan. 31, 2008 Securities Class Action (Policeman's Annuity and Benefit Fund of Chicago) [Member] Defendants	Aug. 31, 2012 Securities Class Action (Policeman's Annuity and Benefit Fund of Chicago) [Member]	Sep. 30, 2011 Securities Class Action (Policeman's Annuity and Benefit Fund of Chicago) [Member]
Loss Contingencies [Line Items]
Number of plaintiffs	3
Number of defendants		2
Agreement in principle settlement amount				$ 145.0
Settlement payment			$ 145.0