Fair Value Measurements Fair Value Measurments (Quantitative Information about Unobservable Inputs) (Details)	6 Months Ended
	May 31, 2013
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liquidity risk premium	4.00%
Market credit default swap spread	2.80%
Credit rating of insurer (in credit rating)	AA-
Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Probability of earning maximum rate until maturity	0.30%
Probability of principal returned prior to maturity	79.10%
Probability of default	4.00%
Recovery rate in default	50.00%
Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Probability of earning maximum rate until maturity	9.40%
Probability of principal returned prior to maturity	95.20%
Probability of default	12.80%
Recovery rate in default	70.00%
Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Probability of earning maximum rate until maturity	1.60%
Probability of principal returned prior to maturity	88.60%
Probability of default	9.80%
Recovery rate in default	56.50%