Debt And Shareholders' Equity (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended		0 Months Ended		9 Months Ended	0 Months Ended			0 Months Ended	9 Months Ended		0 Months Ended	3 Months Ended		9 Months Ended	3 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Preferred Stock [Member]	Sep. 30, 2012 Preferred Stock [Member]	Sep. 30, 2012 Series A Preferred Stock [Member]	Sep. 30, 2012 Series C Preferred Stock [Member]	Mar. 31, 2012 Series D Preferred Stock [Member]	Sep. 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]	Sep. 30, 2012 Fixed Rate Senior Notes [Member]	Mar. 27, 2012 4.5% Senior Unsecured Note [Member]	Sep. 30, 2012 4.5% Senior Unsecured Note [Member]	May 01, 2012 4.5% Senior Unsecured Note [Member]	Jun. 20, 2012 4.0% Senior Unsecured Note [Member]	Sep. 30, 2012 4.0% Senior Unsecured Note [Member]	Aug. 28, 2012 4.0% Senior Unsecured Note [Member]	Jun. 30, 2012 Variable Rate Senior Notes [Member]	Sep. 30, 2012 Long-Term Senior Notes [Member]	Mar. 31, 2012 Long-Term Senior Notes [Member]	Sep. 30, 2012 Long-Term Senior Notes [Member]	Sep. 30, 2012 February 2014 Maturity Notes [Member]	Sep. 30, 2012 June 2014 Maturity Notes [Member]	Sep. 30, 2012 Medium-term Notes [Member]	Sep. 30, 2012 Medium-term Notes [Member]	Sep. 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	1,123,377,000	1,123,377,000	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											553,400,000
Repayments of notes																				254,900,000						7,500,000	74,400,000
Dividends on common stock, per share		0.01
Accretion of redemption discount for preferred stock								33,500,000
Debt issuance amount														300,000,000	400,000,000	100,000,000	158,450,000		20,000,000
Debt issuance amount during period																					91,000,000	5,000,000	29,000,000
Interest rate on senior notes														4.50%			4.00%							3.50%	3.40%			2.00%
Issuance price of seniot notes, percentage of face amount														94.25%		100.249%	97.50%		100.50%
four point zero percent debt issued																		178,450,000
Maturity date of senior medium-term notes														March 27, 2017			June 20, 2016											March 2013
First maturity date for long-term senior medium term notes																								February 2014
Stockholders' Equity [Abstract]
Convertible subordinated debt converted into depositary shares				85,400,000	5,400,000
Convertible preferred stock, shares issued upon conversion						370	84,982
Value added to preferred stock		99,900,000
Intrinsic value of common stock transferred to preferred stock		14,500,000
Common stock outstanding under conversion feature	77,300,000	77,300,000
Accelerated discount amortization	30,400,000	2,000,000
Convertible subordinated debt, at par	462,000,000	462,000,000
Percentage of convertible subordinated debt held by five largest investors	40.00%	40.00%
Debt discount	161,400,000	161,400,000
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