Segment Information - Summary of Segment Information (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Sales Information [Line Items]
Average Assets	$ 89,952	$ 83,662	$ 83,100
Business Banking [Member]
Sales Information [Line Items]
Average Assets	5,287	5,080	5,041
Commercial Banking [Member]
Sales Information [Line Items]
Average Assets	22,805	21,655	21,554
Commercial Real Estate [Member]
Sales Information [Line Items]
Average Assets	16,941	17,150	17,112
Discretionary Portfolio [Member]
Sales Information [Line Items]
Average Assets	20,306	16,480	16,224
Residential Mortgage Banking [Member]
Sales Information [Line Items]
Average Assets	3,262	2,858	2,783
Retail Banking [Member]
Sales Information [Line Items]
Average Assets	10,348	10,997	11,304
Other Segments [Member]
Sales Information [Line Items]
Average Assets	$ 11,003	$ 9,442	$ 9,082