Fair Value Measurement - Level 3 Analysis (Details) (USD $) In Millions, unless otherwise specified		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended				3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Long-term debt	Jun. 30, 2013 Long-term debt	Jun. 30, 2014 Long-term debt	Jun. 30, 2013 Long-term debt	Jun. 30, 2014 Mortgage servicing rights	Jun. 30, 2013 Mortgage servicing rights	Jun. 30, 2014 Mortgage servicing rights	Jun. 30, 2013 Mortgage servicing rights	Jun. 30, 2014 Private equity investments	Jun. 30, 2013 Private equity investments	Jun. 30, 2014 Private equity investments	Jun. 30, 2013 Private equity investments	Jun. 30, 2014 Total net derivative receivables	Jun. 30, 2013 Total net derivative receivables	Jun. 30, 2014 Total net derivative receivables	Jun. 30, 2013 Total net derivative receivables	Jun. 30, 2014 Loans	Jun. 30, 2013 Loans	Jun. 30, 2014 Loans	Jun. 30, 2013 Loans	Jun. 30, 2014 Debt and equity instruments	Jun. 30, 2013 Debt and equity instruments	Jun. 30, 2014 Debt and equity instruments	Jun. 30, 2013 Debt and equity instruments	Jun. 30, 2014 Recurring	Dec. 31, 2013 Recurring	Jun. 30, 2014 Recurring Total net derivative receivables	Jun. 30, 2014 Recurring Total net derivative receivables	Jun. 30, 2014 Recurring Debt and equity instruments	Jun. 30, 2014 Recurring Debt and equity instruments	Jun. 30, 2014 Recurring Level 3	Jun. 30, 2014 Recurring Level 3	Dec. 31, 2013 Recurring Level 3
Level 3 Analysis
Percentage of level 3 assets to total assets	2.50%
Assets measured at fair value on a recurring basis																										$ 762,126	$ 760,327					$ 60,380	$ 60,380	$ 69,310
Increase (decrease) in level 3 assets								(1.3)				(1,600.0)						2,000.0		2,300.0								(4,900.0)	(6,000.0)	1,500.0	(1,400.0)	(2,800.0)	(8,900.0)
Total realized/unrealized gains/(losses)						(149)	1,038	(971)	1,347	168	434	264	165	(1,057)	(77)	(1,430)	844	40	6	72	(29)	902	384	1,552	338
Total realized/unrealized (gains)/losses		$ 437	$ (430)	$ 539	$ (905)