Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Held-to-maturity securities, fair value	$ 4,940	$ 4,974	$ 4,911
Unearned income on loans	645	682	685
Consolidated guaranteed funds VIEs, for accrued income and other assets	1	1	1
Loan securitization trust VIEs		191	201
Loan securitization trust VIEs, fair value	169
Aggregate amount of certificates of deposit, denominations	100,000	100,000	100,000
Consolidated guaranteed funds VIEs, for accrued expenses and other liabilities	$ 1	$ 1	$ 2
Preferred stock, par value	$ 1	$ 1	$ 1
Preferred stock, shares authorized	25,000,000	25,000,000	25,000,000
Common shares, par value	$ 1	$ 1	$ 1
Common shares, shares authorized	1,400,000,000	1,400,000,000	1,400,000,000
Common shares, shares issued	1,016,969,905	1,016,969,905	1,016,969,905
Treasury stock, shares	181,685,035	157,566,493	148,492,881
Series A Preferred Stock [Member]
Preferred stock, liquidation preference	$ 100	$ 100	$ 100
Preferred stock, shares authorized	7,475,000	7,475,000	7,475,000
Preferred stock, shares issued, Total	2,900,234	2,904,839	2,904,839
Preferred stock, dividend rate	7.75%	7.75%	7.75%