Fair Value Measurements (Quantitative Information About Level 3 Measurements) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	$ 9,534	[1]	$ 9,307	[1]
Recurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets at fair value	10,158		9,918
Investment securities available-for-sale	9,534		9,307
Recurring [Member] | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets at fair value	146		162
Investment securities available-for-sale	142		159
Recurring [Member] | State And Municipal Securities | Minimum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input, Discount rate	3.00%	[2]	5.00%	[2]
Unobservable Input, Workout period	1 year	[2]	3 years	[2]
Recurring [Member] | State And Municipal Securities | Maximum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input, Discount rate	10.00%	[2]	10.00%	[2]
Unobservable Input, Workout period	3 years 6 months	[2]	4 years	[2]
Recurring [Member] | Equity and Other Non-Debt Securities | Minimum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input, Discount rate	4.00%	[2]	5.00%	[2]
Unobservable Input, Workout period	1 year	[2]	2 years	[2]
Recurring [Member] | Equity and Other Non-Debt Securities | Maximum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input, Discount rate	8.00%	[2]	8.00%	[2]
Unobservable Input, Workout period	2 years 6 months	[2]	3 years	[2]
State And Municipal Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	23		22
State And Municipal Securities | Recurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	23		22
State And Municipal Securities | Recurring [Member] | State And Municipal Securities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	23	[2]	22	[2]
Equity and Other Non-Debt Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	250		258
Equity and Other Non-Debt Securities | Recurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	250		258
Equity and Other Non-Debt Securities | Recurring [Member] | Equity and Other Non-Debt Securities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	$ 118	[2]	$ 136	[2]

[1] Included auction-rate securities at amortized cost and fair value of $145 million and $142 million, respectively, as of June 30, 2014 and $169 million and $159 million, respectively, as of December 31, 2013.

[2] Auction-rate securities.