Commitments, Contingencies, And Guarantees (Narrative) (Detail) - USD ($) $ in Millions	1 Months Ended
	May 04, 2017	Mar. 31, 2017	Dec. 31, 2016
Financial Instruments Owned and Pledged as Collateral [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed		$ 603
Securities lending collateral		1,071	$ 1,092
Securities lending payable		1,072	1,093
Derivative liability subject to a master netting agreement		1	10
Unrecognized tax benefits		18
Repurchase agreements		1,404	$ 1,403
Funding commitments relating to limited partnerships and partially-owned investment companies		1,900
Carrying value of limited partnerships and partially-owned investment companies included in other investments		$ 3,300
Subsequent Event [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	$ 853
Long-term Purchase Commitment, Amount	$ 250