Subsequent Events (Details) (Subsequent Event [Member], USD $)	0 Months Ended
	Jul. 15, 2013	Jul. 09, 2013 Series F-2 Preferred Stock [Member]	Jul. 09, 2013 Series G Preferred Stock [Member]	Jul. 09, 2013 Series A Preferred Stock [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount	$ 1,400,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Amount	1,000,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.50%
Long-term Debt, Percentage Bearing Variable Interest, Amount	375,000,000
Debt Instrument, Basis Spread on Variable Rate	2.68%
Debt Instrument, Description of Variable Rate Basis	three-month London interbank offer rate
Dividends Payable, Amount Per Share		$ 1.125	$ 17.50	$ 0.53
Dividends Payable		$ 134,000,000	$ 45,000,000	$ 22,000,000