Summary of Significant Accounting Policies (Details) - USD ($) shares in Millions	1 Months Ended		6 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Apr. 30, 2015
Supplemental cash flow information - Noncash activities
Trading assets retained from securitization of MHFS			$ 20,816,000,000	$ 12,373,000,000
Transfers from loans to MHFS			4,757,000,000	6,662,000,000
Transfers from loans to LHFS			52,000,000	9,828,000,000
Transfers from loans to foreclosed and other assets			1,688,000,000	2,268,000,000
Transfers from available-for-sale to held-to-maturity securities			$ 4,972,000,000	0
Private Forward Repurchase Transaction [Member]
Summary Of Significant Accounting Policies Textuals [Abstract]
Private forward repurchase contract				$ 1,000,000,000	$ 750,000,000
Common stock repurchased, shares		19.5
Subsequent Event [Member] | Private Forward Repurchase Transaction [Member]
Summary Of Significant Accounting Policies Textuals [Abstract]
Common stock repurchased, shares	13.6