Debt And Shareholders' Equity (Narrative) (Details) (USD $)	3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended		0 Months Ended		6 Months Ended	0 Months Ended					0 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended				6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Preferred Stock [Member]	Jun. 30, 2012 Preferred Stock [Member]	Jun. 30, 2012 Series A Preferred Stock [Member]	Jun. 30, 2012 Series C Preferred Stock [Member]	Mar. 31, 2012 Series D Preferred Stock [Member] Y	Jun. 30, 2012 Series D Preferred Stock [Member]	Mar. 28, 2012 Series D Preferred Stock [Member]	Jun. 15, 2012 Series E Preferred Stock [Member]	May 07, 2012 Series F Preferred Stock [Member]	Jun. 30, 2012 Fixed Rate Senior Notes [Member]	Mar. 27, 2012 4.5% Senior Unsecured Note [Member]	May 01, 2012 4.5% Senior Unsecured Note [Member]	May 01, 2012 4.5% Senior Unsecured Note [Member] Total Issuance 2012 [Member]	Mar. 27, 2012 4.5% Senior Unsecured Note [Member] First Issuance 2012 [Member]	May 01, 2012 4.5% Senior Unsecured Note [Member] Second Issuance 2012 [Member]	Jun. 20, 2012 4.0% Senior Unsecured Note [Member]	Jun. 30, 2012 Variable Rate Senior Notes [Member]	Jun. 30, 2012 Long-Term Senior Notes [Member]	Jun. 30, 2012 Long-Term Senior Notes [Member]	Jun. 30, 2012 February 2014 Maturity Notes [Member]	Jun. 30, 2012 June 2014 Maturity Notes [Member]	Jun. 30, 2012 Short-Term Senior [Member]	Mar. 31, 2012 Short-Term Senior [Member]	Jun. 30, 2012 Short-Term Senior [Member]
Debt And Shareholders' Equity [Line Items]
Convertible Subordinated Debt Into Depositary Shares		2.50%
Debt [Abstract]
Redemption of cumulative perpetual preferred stock										$ 700,000,000
Cumulative perpetual preferred stock value, issued	1,800,473,000	1,800,473,000	2,377,560,000							1,400,000,000
Preferred stock redemption contingent on specified conditions second installment									700,000,000
Proceeds from issuance of senior notes		600,000,000											533,300,000
Repayments of notes																				254,900,000					12,000,000		66,900,000
Dividends on common stock, per share		0.01
Accretion of redemption discount for preferred stock								19,600,000
Accretion period for unamortized discount (in years)								5
Debt issuance amount																400,000,000	300,000,000	100,000,000	158,450,000
Debt issuance amount during period																					11,900,000	61,900,000				5,000,000
Interest rate on senior notes														4.50%					4.00%				3.50%	3.40%	2.00%		2.00%
Issuance price of seniot notes, percentage of face amount														94.25%	100.249%				97.50%
Maturity date of senior medium-term notes														March 27, 2017					June 20, 2016						March 2013
Maturity date of variable rate senior notes																				June 21, 2012
First maturity date for long-term senior medium term notes																							February 2014
Second maturity date for long-term senior medium term notes																								June 2014
Stockholders' Equity [Abstract]
Convertible subordinated debt converted into depositary shares				50,200,000	80,000,000
Convertible preferred stock, shares issued upon conversion						370	79,596
Value added to preferred stock		93,600,000
Intrinsic value of common stock transferred to preferred stock		13,600,000
Common stock outstanding under conversion feature	78,200,000	78,200,000
Accelerated discount amortization	16,200,000	28,400,000
Convertible subordinated debt, at par	467,400,000	467,400,000
Debt discount	174,000,000	174,000,000
Issuance of preferred stock												143,750,000
Preferred stock, dividend rate											11.00%	7.90%
Preferred stock call date											Jun. 15, 2012
Ownership interest of depositary share in preferred stock share		0.025
Preferred stock redemption value, net											$ 142,500,000