Fair Value, Option, Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Mortgage banking noninterest income [Member] | Trading assets - loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	$ 0	$ 0	$ 0	$ 0
Mortgage banking noninterest income [Member] | Mortgages held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	316	694	897	1,200
Mortgage banking noninterest income [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0	0	0
Mortgage banking noninterest income [Member] | Other assets [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0	0	0
Mortgage banking noninterest income [Member] | Other interests held [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0	0	0
Net gains (losses) from trading activities [Member] | Trading assets - loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	4	6	19	18
Net gains (losses) from trading activities [Member] | Mortgages held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0	0	0
Net gains (losses) from trading activities [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0	0	0
Net gains (losses) from trading activities [Member] | Other assets [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0	0	0
Net gains (losses) from trading activities [Member] | Other interests held [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	(2)	(4)	(2)	(5)
Other noninterest income [Member] | Trading assets - loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	1	2	2	2
Other noninterest income [Member] | Mortgages held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0	0	0
Other noninterest income [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	(39)	1	(43)	1
Other noninterest income [Member] | Other assets [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	(10)	(31)	28	(92)
Other noninterest income [Member] | Other interests held [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	$ 0	$ 1	$ 0	$ 0