Preferred Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended		12 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2013 Series B Preferred Stock [Member]	Jun. 30, 2014 Series C Preferred Stock [Member]	Jun. 30, 2014 Series C Preferred Stock [Member]	Jun. 30, 2014 Common Stock [Member]	Mar. 31, 2014 Common Stock [Member]	Mar. 31, 2013 Common Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Issued	200,000		2,400,000	3,000,000	3,000,000
Preferred Stock, Dividend Rate, Percentage			3.75%	2.50%
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 310.2	$ 234.0	$ 234.0		$ 310.2
Payments of Stock Issuance Costs			7.5		9.8	11.8	12.8
Preferred Stock, Par or Stated Value Per Share			$ 0.01	$ 0.01	$ 0.01
Preferred Stock, Liquidation Preference Per Share			$ 100.00	$ 100.00	$ 100.00
Convertible Preferred Stock, Shares Issued upon Conversion			2.1192	1.8477	1.8477
Conversion price of convertible preferred stock			$ 47.19		$ 54.12
Preferred Stock, Redemption Price, Percentage of Liquidation Preference			100.00%		100.00%
Stock Redemption Triggering Event, Common Stock as Percentage of Conversion Price In Effect			130.00%		150.00%
Stock Redemption Triggering Event, Number of Trading during Thirty Day Consecutive Period, Conversion Price Percentage Met			20 days		20 days
Common Stock, Shares, Issued						0	5,750,000
Common Stock, Par or Stated Value Per Share						$ 0.01
Share Price						$ 47.70	$ 55.00
Proceeds from Issuance of Common Stock	$ 593.4	$ 0				$ 289.9		$ 303.5