Fair Value Measurements Fair Value Measurments (Quantitative Information about Unobservable Inputs) (Details)	3 Months Ended
	Feb. 28, 2013
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liquidity risk premium	4.00%
Market credit default swap spread	3.50%
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	79.90%
Probability of default	3.90%
Recovery rate in default	50.00%
Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Probability of earning maximum rate until maturity	8.70%
Probability of principal returned prior to maturity	95.50%
Probability of default	12.70%
Recovery rate in default	70.00%
Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Probability of earning maximum rate until maturity	1.50%
Probability of principal returned prior to maturity	88.80%
Probability of default	9.60%
Recovery rate in default	57.50%