Loans - Changes in Accretable Yield on Acquired Loans (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Accretable yield, beginning balance	$ 6,420	$ 6,208
Accretion recognized in earnings	(799)	(1,182)
Reclassifications from nonaccretable difference for loans with improving cash flows	105	1,005
Increases (reductions) in accretable yield for non-credit related changes in expected cash flows	(192)	389
Accretable yield, ending balance	5,534	6,420
Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Accretable yield, beginning balance	2,114	1,899
Accretion recognized in earnings	(295)	(427)
Reclassifications from nonaccretable difference for loans with improving cash flows	89	629
Increases (reductions) in accretable yield for non-credit related changes in expected cash flows	(299)	13
Accretable yield, ending balance	1,609	2,114
Non-Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Accretable yield, beginning balance	4,306	4,309
Accretion recognized in earnings	(504)	(755)
Reclassifications from nonaccretable difference for loans with improving cash flows	16	376
Increases (reductions) in accretable yield for non-credit related changes in expected cash flows	107	376
Accretable yield, ending balance	$ 3,925	$ 4,306