Subsequent Events (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Jun. 30, 2012
Series F-2 Preferred Stock [Member]
Subsequent Event [Line Items]
Cash dividend per share	$ 1.125
Preferred stock dividend amount outstanding	$ 134
Series G Preferred Stock [Member]
Subsequent Event [Line Items]
Cash dividend per share	$ 17.50
Preferred stock dividend amount outstanding	45
Series A Preferred Stock [Member]
Subsequent Event [Line Items]
Cash dividend per share	$ 0.53
Preferred stock dividend amount outstanding	$ 22