Fair Value Measurements (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Fair Value Measurements Of Financial Instruments [Line Items]
Total Liabilities Not Carried At Fair Value Not Carried At Fair Value		$ 11,100
Fair Value	$ 3,658	2,477
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Fair Value	$ 3,658	2,477
Minimum [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Notice Period For Redemption For Alternative Investments Investment Funds	5 days
Maximum [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Notice Period For Redemption For Alternative Investments Investment Funds	120 days
Financial Instruments Fair Value [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Total Liabilities Not Carried At Fair Value Not Carried At Fair Value	$ 15,672	$ 11,528