Fair Value Measurements - Fair Value of Direct and Indirect Investments, Related Unfunded Commitments and Financial Support Provided (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Indirect Investments [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair Value	$ 9		$ 9
Unfunded Commitments	1		1
Indirect Investments [Member] | Passive Funds [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair Value	9		9
Unfunded Commitments	1		1
Principal Investments [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair Value	337		337
Unfunded Commitments	53		53
Funded Commitments	2	$ 3	7	$ 10
Funded Other			2	2
Principal Investments [Member] | Indirect Investments [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair Value	271		271
Unfunded Commitments	53		53
Funded Commitments	2	$ 3	7	10
Principal Investments [Member] | Direct Investments [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair Value	$ 66		66
Funded Other			$ 2	$ 2