Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Consolidated Results
Total revenues	$ 11,477	$ 10,425	$ 22,857	$ 20,899
Income (loss) before income taxes	1,102	1,134	2,320	2,024
Shareholders' net income	$ 806	$ 813	$ 1,721	$ 1,411
Shareholders' net income per share:
EPS, basic	$ 3.32	$ 3.2	$ 7.1	$ 5.54
EPS, diluted	3.29	3.15	7.01	5.45
Stock and Dividend Data
Dividends declared per share	$ 0	$ 0	$ 0.04	$ 0.04
Special items
Long-term care guaranty fund assessment			$ 0	$ 83
Transaction-related costs	$ 109	$ (47)	159	2
Total special items	$ 109	$ (47)	$ 159	$ 85