Senior and Subordinated Debt (Details Textuals) (USD $)	3 Months Ended			6 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended					6 Months Ended		6 Months Ended	12 Months Ended			1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended		6 Months Ended	12 Months Ended			3 Months Ended		3 Months Ended	1 Months Ended	6 Months Ended
	Oct. 31, 2011	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011	Jul. 31, 2010	May 12, 2011	Jul. 31, 2011 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Jul. 31, 2010 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Jul. 31, 2011 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Jul. 31, 2010 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Jan. 31, 2011 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Jan. 31, 2010 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Jan. 31, 2009 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Mar. 04, 2010 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Oct. 10, 2006 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Jul. 31, 2011 3.625% Puttable Equity-Linked Senior Notes due 2014 [Member]	Oct. 07, 2009 3.625% Puttable Equity-Linked Senior Notes due 2014 [Member]	Jul. 31, 2011 7.625% Senior Notes due 2015 [Member]	Jan. 31, 2011 7.625% Senior Notes due 2015 [Member]	Mar. 04, 2010 7.625% Senior Notes due 2015 [Member]	May 19, 2003 7.625% Senior Notes due 2015 [Member]	May 31, 2011 5.000% Convertible Senior Notes due 2016 [Member]	Jul. 31, 2011 5.000% Convertible Senior Notes due 2016 [Member]	Jul. 31, 2011 5.000% Convertible Senior Notes due 2016 [Member]	Jan. 31, 2011 5.000% Convertible Senior Notes due 2016 [Member]	May 05, 2011 5.000% Convertible Senior Notes due 2016 [Member]	Oct. 26, 2009 5.000% Convertible Senior Notes due 2016 [Member]	Jul. 31, 2011 4.25% Convertible Senior Notes due 2018 [Member]	Jul. 19, 2011 4.25% Convertible Senior Notes due 2018 [Member]	Jul. 31, 2011 Senior Notes due 2017 [Member]	Jan. 31, 2011 Senior Notes due 2017 [Member]	Mar. 04, 2010 Senior Notes due 2017 [Member]	Jan. 25, 2005 Senior Notes due 2017 [Member]	Jul. 31, 2011 Senior Notes due 2034 [Member]	Feb. 10, 2004 Senior Notes due 2034 [Member]	Jul. 31, 2003 Subordinated Debt [Member]	May 31, 2011 Common Class A [Member]	Jul. 31, 2011 Common Class A [Member]
Debt Instrument [Line Items]
Senior Notes Issued															$ 287,500,000		$ 167,433,000				$ 300,000,000						$ 200,000,000		$ 350,000,000				$ 150,000,000		$ 100,000,000
Interest Rate of Debt Instrument															3.625%		3.625%				7.625%						5.00%		4.25%				6.50%		7.375%	7.875%
Net proceeds from the issuance, net of estimated offering costs				339,375,000																								339,375,000
Reduction in price of senior notes																		100.00%
Purchase of debt instrument											7,000,000		15,000,000																		12,030,000					29,000,000
Senior notes retired											51,176,000								121,747,000												5,826,000
Value of preferred stock exchanged for senior notes														50,664,000						114,442,000												4,894,000
Additional Senior notes issued																	32,567,000
Percentage discount of additional Senior notes issued																	5.00%
Number of Class A Common Stock Shares Received By The Note Holder Upon A Put																68.7758								71.8894				46.1425
Principal amount of notes							1,000		1,000							1,000							1,000	1,000					1,000
Put value price per share									$ 66.39							$ 14.54								$ 13.91
Exercise price of common stock									$ 74.35
Initial put value rate									15.0631
Effective conversion price per share																								$ 16.37
Redemption price of principal amount and accrued interest																																		100.00%
Senior note exchanged for preferred stock series A, value of senior note exchanged														51,176,000						121,747,000												5,826,000
Redemption price of senior notes																		These senior notes may be redeemed by the Company, in whole or in part, at any time on or after June 1, 2008 at an initial redemption price of 103.813% that is systematically reduced to 100% through June 1, 2011.												These senior notes may be redeemed by the Company, in whole or in part, at any time on or after February 1, 2010 at a redemption price of 103.250% beginning February 1, 2010 and systematically reduced to 100% through February 1, 2013. As of February 1, 2011, the redemption price was reduced to 102.167%.
Percentage of the daily volume weighted average price of the Class A common stock has equaled or exceeded the put value price																130.00%												130.00%
Weighted average price of the Class A common stock																$ 18.90												$ 28.17
Increased conversion rate of Convertible Senior Notes due 2016, shares																										86.1073
Loss on early extinguishment of debt	15,200,000	(5,471,000)	1,896,000	(5,767,000)	8,193,000																		10,800,000
Percentage of principal amount of the notes plus accrued and unpaid interest									100.00%
Repayment of debt by issuing Class A common stock				48,742,000																		40,000,000			110,000,000													1,148,000
Outstanding Debt						58,000,000																			90,000,000
Share of Class A common stock																																					3,444,293	3,444,000
Retirement of Common Stock Class A					16,569,000
Conversion Price Per Share																													$ 21.67
Value of senior notes exchanged for new issue of senior notes												167,433,000
Outstanding principal amount of the puttable equity-linked senior notes							46,891,000		46,891,000		46,891,000
Net carrying amount of puttable equity linked senior notes due 2011							46,466,000		46,466,000		45,480,000
Non cash interest expense, senior note due 2011							510,000	358,000	985,000	852,000
Contractual Interest expense, senior notes due 2011							$ 425,000	$ 462,000	$ 850,000	$ 1,151,000
Effective interest rate for the liability component of the puttable equity-linked senior notes due 2011							7.51%	7.51%	7.51%	7.51%