Subsequent Events (Details) (6.50% Series C [Member], USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended
	Mar. 18, 2013	Mar. 19, 2012	Apr. 12, 2013 Subsequent event [Member] Issuance of additional equity in a public offering [Member]
Subsequent Events (Textual) [Abstract]
Common shares issued, net of commissions	3,600,000		400,000
Common shares issued, net of commissions (per share)	$ 25.00		$ 25.00
Net proceeds from issuance of preferred shares		$ 87.1	$ 9.6