INVESTMENTS (DETAILS 4) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Other Investments [Line Items]
Total other investments	$ 699,320,000	$ 519,296,000
Percentage of total fair value	100.00%	100.00%
Percentage subject to lockups	13.00%	8.00%
Total hedge & credit funds currently in liquidation or in a period of planned principal distribution	45,000,000	58,000,000
Multi-strategy Funds [Member] | Quarterly Semi Annually [Member]
Other Investments [Line Items]
Total other investments	230,750,000	256,392,000
Percentage of total fair value	33.00%	49.00%
Percentage subject to lockups	0.00%	4.00%
Multi-strategy Funds [Member] | Quarterly Semi Annually [Member] | Minimum [Member]
Other Investments [Line Items]
Redemption notice period (days)	60	60
Multi-strategy Funds [Member] | Quarterly Semi Annually [Member] | Maximum [Member]
Other Investments [Line Items]
Redemption notice period (days)	95	95
Long/Short Equity Funds [Member] | Quarterly Semi Annually [Member]
Other Investments [Line Items]
Total other investments	214,498,000
Percentage of total fair value	31.00%
Percentage subject to lockups	13.00%
Long/Short Equity Funds [Member] | Quarterly Semi Annually [Member] | Minimum [Member]
Other Investments [Line Items]
Redemption notice period (days)	30
Long/Short Equity Funds [Member] | Quarterly Semi Annually [Member] | Maximum [Member]
Other Investments [Line Items]
Redemption notice period (days)	60
Long/Short Equity Funds [Member] | Quarterly [Member]
Other Investments [Line Items]
Total other investments		50,784,000
Percentage of total fair value		10.00%
Percentage subject to lockups		0.00%
Long/Short Equity Funds [Member] | Quarterly [Member] | Minimum [Member]
Other Investments [Line Items]
Redemption notice period (days)		45
Long/Short Equity Funds [Member] | Quarterly [Member] | Maximum [Member]
Other Investments [Line Items]
Redemption notice period (days)		60
Event Driven Funds [Member] | Quarterly Annually [Member]
Other Investments [Line Items]
Total other investments	118,380,000	73,096,000
Percentage of total fair value	17.00%	14.00%
Percentage subject to lockups	0.00%	4.00%
Event Driven Funds [Member] | Quarterly Annually [Member] | Minimum [Member]
Other Investments [Line Items]
Redemption notice period (days)	45	45
Event Driven Funds [Member] | Quarterly Annually [Member] | Maximum [Member]
Other Investments [Line Items]
Redemption notice period (days)	95	95
Leveraged Bank Loans Funds [Member] | Quarterly Semi Annually [Member]
Other Investments [Line Items]
Total other investments		82,761,000
Percentage of total fair value		16.00%
Percentage subject to lockups		0.00%
Leveraged Bank Loans Funds [Member] | Quarterly Semi Annually [Member] | Minimum [Member]
Other Investments [Line Items]
Redemption notice period (days)		65
Leveraged Bank Loans Funds [Member] | Quarterly Semi Annually [Member] | Maximum [Member]
Other Investments [Line Items]
Redemption notice period (days)		75
Leveraged Bank Loans Funds [Member] | Quarterly [Member]
Other Investments [Line Items]
Total other investments	69,132,000
Percentage of total fair value	10.00%
Redemption notice period (days)	65
Percentage subject to lockups	0.00%
CLO Equity Tranched Securities [Member]
Other Investments [Line Items]
Total other investments	$ 66,560,000	$ 56,263,000
Percentage of total fair value	9.00%	11.00%
Percentage subject to lockups	0.00%	0.00%