Quarterly Financial Data (Unaudited) (Details)		3 Months Ended								12 Months Ended
		Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	Mar. 31, 2014 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares
Disclosure of quarterly financial data
Total revenues net of interest expense | $		$ 8,391,000,000	$ 8,193,000,000	$ 8,284,000,000	$ 7,950,000,000	$ 9,081,000,000	$ 8,303,000,000	$ 8,631,000,000	$ 8,173,000,000	$ 32,818,000,000	$ 34,188,000,000	$ 32,870,000,000
Pretax income | $		1,454,000,000	1,938,000,000	2,230,000,000	2,316,000,000	2,225,000,000	2,246,000,000	2,312,000,000	2,208,000,000	7,938,000,000	8,991,000,000	7,888,000,000
Net income | $		$ 899,000,000	$ 1,266,000,000	$ 1,473,000,000	$ 1,525,000,000	$ 1,447,000,000	$ 1,477,000,000	$ 1,529,000,000	$ 1,432,000,000	$ 5,163,000,000	$ 5,885,000,000	$ 5,359,000,000
Earnings per Common Share
Basic | $ / shares	[1]									$ 5.07	$ 5.58	$ 4.91
Net income attributable to common shareholders | $ / shares		$ 0.89	$ 1.24	$ 1.43	$ 1.49	$ 1.4	$ 1.41	$ 1.44	$ 1.34
Earnings per Common Share
Diluted | $ / shares										5.05	5.56	4.88
Net income attributable to common shareholders | $ / shares		0.89	1.24	1.42	1.48	1.39	1.4	1.43	1.33
Cash dividends declared per common share | $ / shares		$ 0.29	$ 0.29	$ 0.29	$ 0.26	$ 0.26	$ 0.26	$ 0.26	$ 0.23	$ 1.13	$ 1.01	$ 0.89
Common share price:
High | $		77.85	81.66	81.92	93.94	94.89	96.24	96.04	94.35
Low | $		67.57	71.71	76.53	77.12	78.41	85.75	83.99	82.63

[1] Represents net income less ( i ) earnings allocated to participating share awards of $ 38 million, $ 46 million and $ 47 million for the years ended December 31, 2015 , 2014 and 2013 , respectively , and (ii) dividends on preferred shares of $ 62 million for the year ended December 31, 2015 , and nil f or the years ended December 31, 2014 and 2013 .