Debt, Non-Bank Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended						1 Months Ended			3 Months Ended	1 Months Ended							1 Months Ended					1 Months Ended		1 Months Ended			1 Months Ended				3 Months Ended		1 Months Ended				1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Tax Exempt Revenue Refunding Bonds Series 1997B [Member]	Apr. 30, 2011 Tax Exempt Revenue Refunding Bonds Series 1997B [Member]	Apr. 30, 2010 Tax Exempt Revenue Refunding Bonds Series 1997B [Member]	Dec. 31, 2011 Industrial Revenue Bonds Tax Exempt Refunding Bonds [Member]	Apr. 30, 2011 Industrial Revenue Bonds Tax Exempt Refunding Bonds [Member]	Apr. 30, 2010 Industrial Revenue Bonds Tax Exempt Refunding Bonds [Member]	Dec. 31, 2011 Industrial Revenue Bonds Tax Exempt Refunding Bonds [Member]	May 31, 2011 Senior Notes Due In May 2011 [Member]	Dec. 31, 2011 Tax Exempt Revenue Refunding Bonds Series 1997A [Member]	Apr. 30, 2011 Tax Exempt Revenue Refunding Bonds Series 1997A [Member]	Apr. 30, 2010 Tax Exempt Revenue Refunding Bonds Series 1997A [Member]	Dec. 31, 2011 Tax Exempt Revenue Refunding Bonds Series 1997C [Member]	Apr. 30, 2011 Tax Exempt Revenue Refunding Bonds Series 1997C [Member]	Apr. 30, 2010 Tax Exempt Revenue Refunding Bonds Series 1997C [Member]	Feb. 28, 2011 Senior Notes Due In February 2011 [Member]	Dec. 31, 2010 Gulf Opportunity Zone Revenue Bonds Series 2010 [Member]	Mar. 31, 2010 Senior Notes Due In June 2015 [Member]	Feb. 28, 2010 Notes Due In February 2015 [Member]	Dec. 31, 2011 Notes Due In February 2015 [Member]	Feb. 28, 2010 Notes Due In February 2020 [Member]	Dec. 31, 2011 Notes Due In February 2020 [Member]	Feb. 28, 2010 Notes Issued In February 2010 [Member]	Oct. 31, 2009 Senior Notes Due In 2037 [Member]	Dec. 31, 2009 Senior Notes Due In 2037 [Member]	Mar. 31, 2009 Senior Notes Due In March 2019 [Member]	Mar. 31, 2009 Senior Notes Due In March 2039 [Member]	Mar. 31, 2009 Senior Notes Issued In March 2009 [Member]	Feb. 28, 2011 Gulf Opportunity Zone Revenue Bonds Series 2010 [Member]	Dec. 31, 2010 Gulf Opportunity Zone Revenue Bonds Series 2010 [Member]	Dec. 31, 2011 Gulf Opportunity Zone Revenue Bonds Series 2010 [Member]	Jun. 30, 2010 Debenture Due In June 2010 [Member]	May 31, 2010 Senior Notes Due In May 2014 [Member]	Oct. 31, 2009 Senior Notes Due In 2037 [Member]	Dec. 31, 2011 Senior Notes Due In 2037 [Member]	Apr. 30, 2009 Notes Due In April 2009 [Member]	Apr. 30, 2009 Tax Exempt Revenue Refunding Bonds Series 1997D [Member]
Non-Bank Debt (Textual)
Interest rate of notes in percentage				5.40%	5.40%	5.40%					6.125%	5.45%	5.45%	5.45%	5.40%	5.40%	5.40%	6.75%		7.50%	4.50%	4.50%	6.125%	6.125%			6.75%	9.375%	10.50%					7.25%	6.75%		6.75%	3.50%	5.125%
Debt repayments	$ 774	$ 517	$ 285					$ 8	$ 8	$ 56	$ 200							$ 210		$ 294						$ 76					$ 300			$ 25	$ 190			$ 200	$ 9
Redemption value in percentage							100.00%													102.50%															102.25%	100.00%
Notes issued, face amount																					400		850					750	250
Revenue bond																																300	0
Debt instrument maturity date (month, day, year)																				Jun. 15, 2015	Feb. 01, 2015		Feb. 01, 2020			Oct. 15, 2037		Mar. 15, 2019	Mar. 15, 2039			Dec. 01, 2040			May 01, 2014
Proceeds from debt, net of issuance costs	$ 0	$ 1,544	$ 998																$ 300						$ 1,200					$ 998