Shareholders' Equity (Narrative) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		12 Months Ended	0 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2014 item	Mar. 31, 2013	Dec. 31, 2013	Mar. 14, 2013 Series V [Member]	Mar. 31, 2014 Series V [Member]	Dec. 31, 2013 Series V [Member]
Class of Stock [Line Items]
Cumulative preferred stock, dividend rate				5.70%	5.70%	5.70%
Issuance Date					Mar. 14, 2013	Mar. 14, 2013
Proceeds from issuance of depositary shares	$ 995,000,000		$ 995,000,000	$ 110,000,000	$ 110,000,000	$ 110,000,000
Depositary shares issued				4.4
Depository shares conversion ratio to preferred share				0.001%
Depositary shares issued price per share				$ 25.00
Distributions recorded to preferred shareholders	15,100,000	13,900,000
Number of quarterly dividends in arrearage before preferred shareholders can elect additional board members	6
Number of additional board members the preferred shareholders can elect in the case of an excess arrearage of quarterly dividends	2
Dividends in arrears	0
Redeemable preferred stock, redemption price per share	$ 25.00
Preferred stock, aggregate deferred issuance costs outstanding	$ 31,800,000		$ 31,800,000