Securities Available for Sale and Securities Held to Maturity (Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Securities Available for Sale) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	$ 51,940		$ 51,604
Securities available for sale Gross Unrealized Gains	379		255
Securities available for sale Gross Unrealized Losses	118		241
Securities available for sale	52,201		51,618
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	19,419		15,201
Securities available for sale Gross Unrealized Gains	90		42
Securities available for sale Gross Unrealized Losses	6		37
Securities available for sale	19,503		15,206
U.S. agency mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	18,001		18,554
Securities available for sale Gross Unrealized Gains	215		140
Securities available for sale Gross Unrealized Losses	15		49
Securities available for sale	18,201	[1]	18,645
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	7,644		8,973
Securities available for sale Gross Unrealized Gains	46		49
Securities available for sale Gross Unrealized Losses	6		15
Securities available for sale	7,684		9,007
U.S. agency notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	3,990		4,239
Securities available for sale Gross Unrealized Gains			1
Securities available for sale Gross Unrealized Losses	67		104
Securities available for sale	3,923		4,136
Certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	1,533		3,650
Securities available for sale Gross Unrealized Gains	1		4
Securities available for sale Gross Unrealized Losses			2
Securities available for sale	1,534		3,652
Non-agency residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	543		616
Securities available for sale Gross Unrealized Gains	19		11
Securities available for sale Gross Unrealized Losses	24		34
Securities available for sale	538	[1]	593
Non-agency commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	311		271
Securities available for sale Gross Unrealized Gains	7		8
Securities available for sale	318	[1]	279
Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost	499
Securities available for sale Gross Unrealized Gains	1
Securities available for sale	500
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available for sale Amortized Cost			100
Securities available for sale			$ 100

[1] Mortgage-backed securities have been allocated to maturity groupings based on final contractual maturities. Actual maturities will differ from final contractual maturities because borrowers on a certain portion of loans underlying these securities have the right to prepay their obligations.