Convertible Senior Notes (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended				1 Months Ended	12 Months Ended
	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2012 Level 2	Apr. 30, 2012 Convertible Senior Notes	Nov. 30, 2012 Convertible Senior Notes
Debt Instrument [Line Items]
Principle amount of senior note					$ 600,000,000
Debt instrument, fixed annual interest rate					2.25%
Principal amount of note					1,000
Convertible senior notes conversion ratio					19.7750
Convertible senior notes initial conversion price					$ 50.57
Convertible senior notes minimum number of days out of thirty that common stock price exceeded conversion price						20 days
Convertible senior notes number of consecutive trading days						30 days
Convertible senior notes minimum percentage of conversion price						130.00%
Consecutive trading day period	5 days
Convertible senior notes maximum percentage of trading price						98.00%
Stock observation period	35 days
Payments classification for shares repurchased	220,265,000	194,059,000	204,280,000			121,000,000
Shares repurchased						3,600
Debt effective interest rate						5.50%
Debt discount, after tax	(50,833,000)					52,600,000
Debt discount, before tax					84,600,000	75,500,000
Convertible senior notes, net	524,466,000	0				524,500,000
Deferred issuance costs					15,600,000
Deferred issuance costs, liability component					13,400,000
Deferred issuance costs, equity component					2,200,000
Deferred issuance costs, equity component net of tax					1,400,000
Interest Expense	23,396,000	4,020,000	4,123,000			18,800,000
Convertible note contractual coupon interest						8,200,000
Amortization of debt discount						9,000,000
Amortization of debt issuance costs						1,600,000
Convertible senior notes, fair value disclosures				$ 583,000,000