Other Short-Term Borrowings (Components of Other Short-Term Borrowings) (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Short Term Debt
FHLB advances	$ 400	$ 3,125
Securities sold under repurchase agreements	662	546
Derivative collateral	273	341
Total other short-term borrowings	$ 1,335	$ 4,012