Debt And Shareholders' Equity (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended			3 Months Ended	1 Months Ended	3 Months Ended			0 Months Ended		0 Months Ended				3 Months Ended
	May 01, 2012	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Mar. 31, 2012 Series A Preferred Stock [Member]	Apr. 18, 2012 Series C Preferred Stock [Member]	Mar. 31, 2012 Series C Preferred Stock [Member]	Mar. 31, 2012 Series D Preferred Stock [Member] Y	Mar. 28, 2012 Series D Preferred Stock [Member]	Jun. 15, 2012 Series E Preferred Stock [Member]	Mar. 31, 2012 Preferred Stock [Member]	May 07, 2012 Series F Preferred Stock [Member]	May 01, 2012 4.5% Senior Unsecured Note [Member]	Mar. 27, 2012 4.5% Senior Unsecured Note [Member]	Mar. 31, 2012 Variable Rate Senior [Member]	Mar. 31, 2012 Short-Term Senior [Member]	Mar. 31, 2012 Long-Term Senior [Member]
Debt And Shareholders' Equity [Line Items]
Redemption of Cumulative Perpetual Preferred Stock									$ 700,000,000
Cumulative perpetual preferred stock value, issued		1,737,633,000		2,377,560,000					1,400,000,000
Preferred stock redemption contingent on specified conditions second installment								700,000,000
Issuance of senior debt	400,000,000	600,000,000											100,000,000
Dividends on common stock, per share		$ 0.01	$ 0.01
Accretion of redemption discount for preferred stock								19,600,000
Accretion period for unamortized discount (in years)								5
Preferred stock redemption value, net								700,000,000		142,500,000
Senior medium-term notes issued														300,000,000	254,900,000	5,000,000	50,000,000
Maturity date of senior medium-term notes														March 27, 2017		March 2013	February 2014
Sale of notes, percentage													100.25%	94.25%
Net proceeds, sale of notes													99,900,000	280,500,000
Interest rate on senior notes													4.50%	4.50%		2.00%	3.50%
Preferred stock call date										Jun. 15, 2012
Preferred stock, dividend rate										11.00%		7.90%
Issuance of preferred stock												143,750,000
Convertible preferred stock, shares issued upon conversion					370		29,404
Convertible subordinated debt converted into depositary shares		1/40th
Convertible subordinated debt											29,800,000
Convertible subordinated debt converted into depositary shares, value		29,774,000	85,849,000
Common stock outstanding under conversion feature		86,800,000
Convertible subordinated debt, at par		517,600,000
Value added to preferred stock		34,800,000
Accelerated discount amortization		12,200,000
Sale of common stock		350,000,000		350,000,000
Proceeds from issuance of common stock		342,000	25,212,000
Debt discount		200,800,000
Intrinsic value of common stock transferred to preferred stock		5,100,000
Approximate value of subordinated convertible notes converted into preferred stock						$ 50,200,000
Preferred stock issued for conversion of subordinated notes						50,192