Other Securities Owned (Summary of Other Securities Owned) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Securities Owned [Line Items]
Other securities owned	$ 539	$ 449
Equity and bond mutual funds [Member]
Other Securities Owned [Line Items]
Other securities owned	318	272
Schwab Funds money market funds [Member]
Other Securities Owned [Line Items]
Other securities owned	135	108
State and municipal debt obligations [Member]
Other Securities Owned [Line Items]
Other securities owned	52	41
Equity, U.S. Government and corporate debt, and other securities [Member]
Other Securities Owned [Line Items]
Other securities owned	$ 34	$ 28