Fair Values of Assets and Liabilities Textuals (Details) $ in Millions	6 Months Ended			12 Months Ended
	Jun. 30, 2015 USD ($) $ / loan		Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) $ / loan
Fair Values of Assets and Liabilities (Textual) [Abstract]
Net unrealized gains (losses) on trading securities	$ (470)		$ 216	$ 211
Available-for-sale, at fair value	260,667			257,442
Mortgages held for sale	21,539			15,565
FV of NMEI in private equity funds where nonrecurring FV adjustments were recorded	0			171
Fair Value of cost method NMEI using NAV	1,000			1,300
Fair Value of NMEI using NAV	125			108
Loans	888,459	[1]		862,551
Capital lease obligation	8			9
Estimated fair value [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Loans	867,733			844,838
Loan commitments, standby letters of credit and similar letters of credit	$ 949			945
Private Equity Funds [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Alternative Investment, Distributions From Underlying Assets, Distribution Period	6 years
Venture Capital Funds [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Investment Fund Liquidation Period	4 years
Offshore Funds [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Redemption restriction for investment	$ 24			24
Fair Value, Measurements, Recurring [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Available-for-sale, at fair value	260,667			257,442
Total assets recorded at fair value	386,736			378,099
Total liabilities recorded at fair value	30,629			34,866
Mortgages held for sale	21,539			15,565
Fair Value, Inputs, Level 3 [Member] | Estimated fair value [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Loans	807,430			784,786
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Available-for-sale, at fair value	4,830			6,029
Total assets recorded at fair value	29,871			32,324
Total liabilities recorded at fair value	2,000			2,270
Mortgages held for sale	1,623			2,313
Lease Financing [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Loans	12,201			12,307
Residential [Member] | Government Insured Or Guaranteed [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Mortgages held for sale	904			1,000
Residential [Member] | Non Government Insured Or Guaranteed [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Mortgages held for sale	$ 51			$ 78
Maximum [Member] | Non modified loans [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Cost to service per loan | $ / loan	369			270
Minimum [Member] | Non modified loans [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Cost to service per loan | $ / loan	68			86
Collateralized debt obligations [Member]
Fair Values of Assets and Liabilities (Textual) [Abstract]
Available-for-sale, at fair value	$ 407			$ 500
Trading and available for sale securities	$ 407			$ 500

[1] Parenthetical amounts represent assets and liabilities for which we have elected the fair value option.