Senior and Subordinated Debt (Details Textual) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended	1 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		1 Months Ended	9 Months Ended		9 Months Ended
	Oct. 31, 2011	Oct. 31, 2010	Oct. 31, 2011	Oct. 31, 2010	Jan. 31, 2011	May 31, 2011 Common Class A [Member]	Oct. 31, 2011 Common Class A [Member]	Jan. 31, 2011 Common Class A [Member]	Oct. 31, 2011 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Oct. 31, 2010 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Oct. 31, 2011 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	Oct. 31, 2010 3.625% Puttable Equity-Linked Senior Notes due 2011 [Member]	May 31, 2011 5.000% Convertible Senior Notes due 2016 [Member]	Oct. 31, 2011 5.000% Convertible Senior Notes due 2016 [Member]	May 05, 2011 5.000% Convertible Senior Notes due 2016 [Member]	Oct. 31, 2011 4.25% Convertible Senior Notes due 2018 [Member]	Jul. 19, 2011 4.25% Convertible Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Senior Notes Issued																	$ 350,000,000
Interest Rate									3.625%		3.625%				5.00%		4.25%
Effective interest rate for the liability component of the puttable equity-linked senior notes due 2011									7.51%	7.51%	7.51%	7.51%
Non cash interest expense, senior note due 2011									426,000	322,000	1,411,000	1,174,000
Contractual Interest expense, senior notes due 2011									354,000	425,000	1,204,000	1,576,000
Repayment of debt by issuing Class A common stock			48,742,000		136,444,000		1,148,000	3,258,000					40,000,000
Number of Class A Common Stock Shares Received By The Note Holder Upon A Put														71.8894		46.1425
Principal amount of notes														$ 1,000			$ 1,000
Increased conversion rate of Convertible Senior Notes due 2016, shares															86.1073
Share of Class A common stock						3,444,293	3,444,000	9,774,000
Loss on early extinguishment of debt	15,101,000	2,460,000	9,334,000	10,653,000										(10,800,000)
Conversion Price Per Share																	$ 21.67
Percentage of the daily volume weighted average price of the Class A common stock has equaled or exceeded the put value price																130.00%
Minimum trading days during which daily volume weighted average price exceeds or equal put value price																At least 20 days within a 30 day period
Weighted Average Price of Common Stock Equaled or Exceeded Put Value Price																$ 28.17