Financial Instruments (Details Textual) (USD $)	3 Months Ended
	Feb. 29, 2012	Feb. 28, 2011	Nov. 30, 2011
Investment Holdings [Line Items]
Investments, at fair value	$ 105,719,000		$ 105,585,000
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	109,900,000	26,800,000
Transfers of assets from Level 3 to Level 2	41,500,000	8,500,000
Financial Instruments (Textual) [Abstract]
Investments, at fair value	105,719,000		105,585,000
Transfers of liabilities from Level 2 to Level 3	0
Transfers of liabilities from Level 3 to Level 2	2,200,000	0
Net gains/losses on Level 3 assets (realized and unrealized)	9,700,000	48,800,000
Net gains/losses on Level 3 liabilities (realized and unrealized)	1,500,000	2,600,000
Aggregate fair value of loans	800,000		5,500,000
Loans receivable fair value description	90 or more days
Loans or other receivables on nonaccrual status	0		0
Financial instruments issuance	0
Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	42,800,000	1,216,000
Financial Instruments (Textual) [Abstract]
Net gains/losses on Level 3 assets (realized and unrealized)	(796,000)	10,310,000
Residential mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	32,500,000	12,886,000
Transfers of assets from Level 3 to Level 2	6,600,000	(40,000)
Financial Instruments (Textual) [Abstract]
Net gains/losses on Level 3 assets (realized and unrealized)	(6,492,000)	16,205,000
Other asset-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	4,700,000	11,050,000
Transfers of assets from Level 3 to Level 2	2,300,000	(567,000)
Financial Instruments (Textual) [Abstract]
Net gains/losses on Level 3 assets (realized and unrealized)	(104,000)	(215,000)
Commercial mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	1,500,000
Transfers of assets from Level 3 to Level 2	12,800,000	(2,729,000)
Financial Instruments (Textual) [Abstract]
Net gains/losses on Level 3 assets (realized and unrealized)	(1,655,000)	222,000
Loans and other receivables [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	18,400,000	1,574,000
Transfers of assets from Level 3 to Level 2	13,900,000	(368,000)
Financial Instruments (Textual) [Abstract]
Net gains/losses on Level 3 assets (realized and unrealized)	1,899,000	5,974,000
Corporate debt securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	8,600,000	106,000
Transfers of assets from Level 3 to Level 2	500,000	(520,000)
Financial Instruments (Textual) [Abstract]
Net gains/losses on Level 3 assets (realized and unrealized)	671,000	2,283,000
Corporate equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	900,000
Transfers of assets from Level 3 to Level 2		(1,277,000)
Financial Instruments (Textual) [Abstract]
Net gains/losses on Level 3 assets (realized and unrealized)	1,684,000	5,167,000
Municipal securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	500,000
Transfers of assets from Level 3 to Level 2	5,400,000
Financial Instruments (Textual) [Abstract]
Net gains/losses on Level 3 assets (realized and unrealized)	(71,000)	19,000
Private Equity Funds [Member]
Investment Holdings [Line Items]
Percentage of investments at fair value expected to liquidate	96.00%		96.00%
Investments Period Estimated To Be Liquidated	One to eight years
Croatian and Vietnamese companies [Member]
Investment Holdings [Line Items]
Percentage of investments at fair value expected to liquidate	4.00%		4.00%
Investments Which are Not Investment Companies [Member]
Investment Holdings [Line Items]
Investments, at fair value	57,100,000		55,900,000
Financial Instruments (Textual) [Abstract]
Investments, at fair value	$ 57,100,000		$ 55,900,000
Funds of Funds [Member]
Investment Holdings [Line Items]
Percentage of Irredeemable Investments	99.00%		95.00%
Percentage of investments at fair value expected to liquidate	1.00%		5.00%
Investments Period Estimated To Be Liquidated	One to two years
Equity Long/Short Hedge Funds [Member]
Investment Holdings [Line Items]
Percentage of Redeemable Investments	98.00%		98.00%
Percentage of Irredeemable Investments	2.00%		2.00%
Investments period estimated to be liquidated	less than 1%		less than 1%
Percentage of investment with no redemption provisions	0.00%
Notice period redemption of investments prior written notice period	30-65 days
Investments Period Estimated To Be Liquidated	One to two years
Convertible Bonds [Member]
Investment Holdings [Line Items]
Redeemable period of investments	5 days