Receivable from Mutual Funds, Insurance Companies, and Other - Composition of Partnership's Receivable from Mutual Funds, Insurance Companies and Other (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Brokers And Dealers [Abstract]
Deposit for Canadian retirement accounts	$ 257	$ 236
Asset-based fees from mutual fund and insurance companies	238	224
Fees for shareholder accounting services from mutual fund companies	45	53
Total	$ 540	$ 513