Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Consolidated Results
Total revenues	$ 10,318	$ 9,960	$ 20,703	$ 19,844
Income before income taxes	1,134	813	2,024	1,632
Shareholders' net income	$ 813	$ 510	$ 1,411	$ 1,029
Shareholders' Net Income Per Share:
EPS, basic	$ 3.2	$ 2	$ 5.54	$ 4.03
EPS, diluted	3.15	1.97	5.45	3.97
Stock and Dividend Data
Dividends Declared Per Share	$ 0	$ 0	$ 0.04	$ 0.04
Special items
Merger-related transaction costs	$ (47)	$ 26	$ 2	$ 62