Contingencies and Other Matters - Legal and Regulatory Matters (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2016
Loss Contingencies [Line Items]
Total revenues	$ 9,880	$ 9,389	$ 29,724	$ 28,348
Shareholders' net income	456	$ 547	1,485	1,668
CMS Actions [Member]
Loss Contingencies [Line Items]
Costs related to CMS audit response, after-tax			$ 80
CMS Actions [Member] | Scenario, Forecast [Member]
Loss Contingencies [Line Items]
Total revenues
Shareholders' net income
Disability Claims Regulatory Matter [Member]
Loss Contingencies [Line Items]
Monitoring period			2 years
Guaranty Fund Assessments [Member]
Loss Contingencies [Line Items]
Charges related to guaranty fund assessments
Estimate of possible loss	80		80
Pending Litigation [Member]
Loss Contingencies [Line Items]
Reserves for litigation matters, pre-tax	230		230
Reserves for litigation matters, after-tax	$ 150		$ 150