Schedule of Contractual Maturities of Debt Securities Available for Sale (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Available-for-sale Securities, Debt Maturities [Abstract]
Due within one year, Amortized Cost	$ 422
Due after one year through five years, Amortized Cost	2,144
Due after five years through ten years, Amortized Cost	2,264
Due after ten years, Amortized Cost	1,942
Mortgage and asset-backed securities, Amortized Cost	2,187
Total debt securities, Amortized Cost	8,959	9,550
Due within one year, Fair Value	427
Due after one year through five years, Fair Value	2,268
Due after five years through ten years, Fair Value	2,413
Due after ten years, Fair Value	2,124
Mortgage and asset-backed securities, Fair Value	2,228
Total debt securities, Fair Value	$ 9,460	$ 9,800