Investment Securities - Gross Unrealized Losses and Fair Value of Company's Investments Securities with Unrealized Losses (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	$ 20,621
Unrealized Losses Less Than 12 Months	(407)
Fair Value 12 Months or Greater	23
Unrealized Losses 12 Months or Greater	(15)
Fair Value Total	20,644
Unrealized Losses Total	(422)
Fair Value Less Than 12 Months	13,562
Unrealized Losses Less Than 12 Months	(371)
Fair Value 12 Months or Greater	1,233
Unrealized Losses 12 Months or Greater	(115)
Fair Value Total	14,795
Unrealized Losses Total	(486)
U.S. Treasury and agencies [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	969
Unrealized Losses Less Than 12 Months	(48)
Fair Value 12 Months or Greater
Unrealized Losses 12 Months or Greater
Fair Value Total	969
Unrealized Losses Total	(48)
Fair Value Less Than 12 Months	945
Unrealized Losses Less Than 12 Months	(38)
Fair Value 12 Months or Greater
Unrealized Losses 12 Months or Greater
Fair Value Total	945
Unrealized Losses Total	(38)
Residential [Member] | Agency [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	19,643
Unrealized Losses Less Than 12 Months	(358)
Fair Value 12 Months or Greater
Unrealized Losses 12 Months or Greater
Fair Value Total	19,643
Unrealized Losses Total	(358)
Fair Value Less Than 12 Months	11,641
Unrealized Losses Less Than 12 Months	(298)
Fair Value 12 Months or Greater	350
Unrealized Losses 12 Months or Greater
Fair Value Total	11,991
Unrealized Losses Total	(298)
Residential [Member] | Residential Non-Agency Prime [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	129
Unrealized Losses Less Than 12 Months	(2)
Fair Value 12 Months or Greater	225
Unrealized Losses 12 Months or Greater	(12)
Fair Value Total	354
Unrealized Losses Total	(14)
Residential [Member] | Residential Non-Agency Non-Prime [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	24
Unrealized Losses Less Than 12 Months
Fair Value 12 Months or Greater	102
Unrealized Losses 12 Months or Greater	(6)
Fair Value Total	126
Unrealized Losses Total	(6)
Asset Backed Securities Other [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months
Unrealized Losses Less Than 12 Months
Fair Value 12 Months or Greater	10
Unrealized Losses 12 Months or Greater	(2)
Fair Value Total	10
Unrealized Losses Total	(2)
Fair Value Less Than 12 Months
Unrealized Losses Less Than 12 Months
Fair Value 12 Months or Greater	2
Unrealized Losses 12 Months or Greater	(1)
Fair Value Total	2
Unrealized Losses Total	(1)
Obligations of state and political subdivisions [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	8
Unrealized Losses Less Than 12 Months	(1)
Fair Value 12 Months or Greater
Unrealized Losses 12 Months or Greater
Fair Value Total	8
Unrealized Losses Total	(1)
Fair Value Less Than 12 Months	596
Unrealized Losses Less Than 12 Months	(32)
Fair Value 12 Months or Greater	10
Unrealized Losses 12 Months or Greater
Fair Value Total	606
Unrealized Losses Total	(32)
Obligations of foreign governments [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	6
Unrealized Losses Less Than 12 Months
Fair Value 12 Months or Greater
Unrealized Losses 12 Months or Greater
Fair Value Total	6
Unrealized Losses Total
Corporate debt securities [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	218
Unrealized Losses Less Than 12 Months	(1)
Fair Value 12 Months or Greater	426
Unrealized Losses 12 Months or Greater	(81)
Fair Value Total	644
Unrealized Losses Total	(82)
Perpetual preferred securities [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months
Unrealized Losses Less Than 12 Months
Fair Value 12 Months or Greater	118
Unrealized Losses 12 Months or Greater	(15)
Fair Value Total	118
Unrealized Losses Total	(15)
Other investments [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	3
Unrealized Losses Less Than 12 Months
Fair Value 12 Months or Greater
Unrealized Losses 12 Months or Greater
Fair Value Total	3
Unrealized Losses Total
Commercial [Member] | Non-Agency [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months	1
Unrealized Losses Less Than 12 Months
Fair Value 12 Months or Greater
Unrealized Losses 12 Months or Greater
Fair Value Total	1
Unrealized Losses Total
Other debt securities [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Abstract]
Fair Value Less Than 12 Months
Unrealized Losses Less Than 12 Months
Fair Value 12 Months or Greater	13
Unrealized Losses 12 Months or Greater	(13)
Fair Value Total	13
Unrealized Losses Total	$ (13)