Fair Value Measurements - Fair Value of Direct and Indirect Investments, Related Unfunded Commitments and Financial Support Provided (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2015
Minimum [Member] | Passive Funds [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Liquidation period of funds	1 year
Minimum [Member] | Indirect Investments [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Liquidation period of funds	1 year
Maximum [Member] | Passive Funds [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Liquidation period of funds	4 years
Maximum [Member] | Indirect Investments [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Liquidation period of funds	9 years